Following the work done by @jdevlieghere in D143690, this changes how Clang module build
events are emitted.
Instead of one Progress event per module being built, a single Progress event is used to
encompass all modules, and each module build is sent as an `Increment` update.
Differential Revision: https://reviews.llvm.org/D147248
Update the Clang diagnostic consumer (in ClangModulesDeclVendor) to report
progress on Clang module builds, as both progress events and expression logs.
Module build remarks are enabled by with clang's `-Rmodule-build` flag.
With this change, command line users of lldb will see progress events showing
which modules are being built, and - by how long they stay on screen - how much
time it takes to build them. IDEs that show progress events can show these
updates if desired.
This does not show module-import remarks, although that may be added as a
future change.
Differential Revision: https://reviews.llvm.org/D140056
