Reverts llvm/llvm-project#153756
It leads to new build bot failure.
https://lab.llvm.org/buildbot/#/builders/145/builds/9200
```
BUILD FAILED: failed build (failure)
Step 5 (build-unified-tree) failure: build (failure) ...
254.983 [140/55/1504] Building CXX object tools/clang/tools/extra/clangd/tool/CMakeFiles/obj.clangdMain.dir/ClangdMain.cpp.o
FAILED: tools/clang/tools/extra/clangd/tool/CMakeFiles/obj.clangdMain.dir/ClangdMain.cpp.o
ccache /home/buildbots/llvm-external-buildbots/clang.19.1.7/bin/clang++ --gcc-toolchain=/gcc-toolchain/usr -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/tools/clang/tools/extra/clangd/tool -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/tool -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/../include-cleaner/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/tools/clang/tools/extra/clangd/../clang-tidy -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-
rhel-test/clang-ppc64le-rhel/build/tools/clang/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/tools/clang/tools/extra/clangd -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe -unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -Wno-nested-anon-types -O3 -DNDEBUG -std=c++17 -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT tools/clang/tools/extra/clangd/tool/CMakeFiles/obj.clangdMain.dir/ClangdMain.cpp.o -MF tools/clang/tools/extra/clangd/tool/CMakeFiles/obj.clangdMain.dir/ClangdMain.cpp.o.d -o tools/clang/tools/extra/clangd/tool/CMakeFiles/obj.clangdMain.dir/ClangdMain.cpp.o -c /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/tool/ClangdMain.cpp
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/tool/ClangdMain.cpp:10:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/ClangdLSPServer.h:12:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/ClangdServer.h:12:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/CodeComplete.h:18:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/ASTSignals.h:12:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/ParsedAST.h:23:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/CollectMacros.h:12:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/Protocol.h:26:
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/URI.h:14:
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/include/llvm/Support/Registry.h:110:47: error: instantiation of variable 'llvm::Registry<clang::clangd::FeatureModule>::Head' required here, but no definition is available [-Werror,-Wundefined-var-template]
110 | static iterator begin() { return iterator(Head); }
| ^
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/include/llvm/Support/Registry.h:114:25: note: in instantiation of member function 'llvm::Registry<clang::clangd::FeatureModule>::begin' requested here
114 | return make_range(begin(), end());
| ^
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang-tools-extra/clangd/tool/ClangdMain.cpp:1021:64: note: in instantiation of member function 'llvm::Registry<clang::clangd::FeatureModule>::entries' requested here
1021 | for (FeatureModuleRegistry::entry E : FeatureModuleRegistry::entries()) {
| ^
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/include/llvm/Support/Registry.h:61:18: note: forward declaration of template entity is here
61 | static node *Head;
| ^
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/include/llvm/Support/Registry.h:110:47: note: add an explicit instantiation declaration to suppress this warning if 'llvm::Registry<clang::clangd::FeatureModule>::Head' is explicitly instantiated in another translation unit
110 | static iterator begin() { return iterator(Head); }
| ^
1 error generated.
```
I need some time to fix this in a correct way
This patch adds feature modules registry, as discussed with @kadircet in
[discourse](https://discourse.llvm.org/t/rfc-registry-for-feature-modules/87733).
Feature modules, which added into the feature module set from registry
entries, can't expose public API, but still can be used via
`FeatureModule` interface.
As pointed out in D96244, "Module" is already pretty overloaded to refer
to clang and llvm modules. (And clangd deals directly with the former).
FeatureModule is a bit of a mouthful but it's pretty self-descriptive.
I think it might be better than "Component" which doesn't really capture
the "common interface" aspect - it's IMO confusing to refer to
"components" but exclude CDB for example.
Differential Revision: https://reviews.llvm.org/D97950
