tools: Remove untested PluginLoader includes (#117644)

As far as I can tell there are 2 parallel plugin mechanisms.
opt -load=plugin does not work, and is ignored. opt -load-pass-plugin
does work. PluginLoader.h forces a static definition of the "load"
cl::opt into included TUs. Delete the cases with no tests.

llvm/docs/CommandGuide/llc.rst

@@ -140,12 +140,6 @@ End-user Options
  Record the amount of time needed for each pass and print a report to standard
  error.
 
-.. option:: --load=<dso_path>
-
- Dynamically load ``dso_path`` (a path to a dynamically shared object) that
- implements an LLVM target.  This will permit the target name to be used with
- the :option:`-march` option so that code can be generated for that target.
-
 .. option:: -meabi=[default|gnu|4|5]
 
  Specify which EABI version should conform to.  Valid EABI versions are *gnu*,

llvm/docs/CommandGuide/lli.rst

@@ -43,11 +43,6 @@ GENERAL OPTIONS
 
  Print a summary of command line options.
 
-.. option:: -load=pluginfilename
-
- Causes :program:`lli` to load the plugin (shared object) named *pluginfilename* and use
- it for optimization.
-
 .. option:: -stats
 
  Print statistics from the code-generation passes. This is only meaningful for

llvm/tools/llc/llc.cpp

@@ -49,7 +49,6 @@
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/PGOOptions.h"
 #include "llvm/Support/Path.h"
-#include "llvm/Support/PluginLoader.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/TimeProfiler.h"

llvm/tools/lli/lli.cpp

@@ -60,7 +60,6 @@
 #include "llvm/Support/Memory.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
-#include "llvm/Support/PluginLoader.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/SourceMgr.h"