[bazel] Add missing clang/unittests targets (#150491)

Mostly just adding tests that are in clang/unittests/CMakeLists.txt, but
there a couple other cleanups here:
* Add `directory_watcher` targets in clang so we can add tests for it
* Add some library targets (e.g. `dataflow_testing_support`) for
downstream use (e.g. unit tests outside of LLVM that use these headers
in tests)
* Remove `rename_tests_tooling_hdrs` which has been unused since
`rename_tests` itself was deleted

The InterpreterTest target added here passes on our internal CI, but
fails when I run it w/ bazel for some reason:
```
[ RUN      ] InterpreterTest.InstantiateTemplate
JIT session error: Symbols not found: [ __clang_Interpreter_SetValueWithAlloc, _ZnwmPv26__clang_Interpreter_NewTag ]
Failure value returned from cantFail wrapped call
Failed to materialize symbols: { (main, { __orc_init_func.incr_module_133, $.incr_module_133.__inits.0 }) }
```
I'd like to figure out what's going on, but for now I just excluded it
w/ a test filter
2 files changed
tree: 2d44596fc08d01ca8c9fc391d95782a4d279ae9b
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libunwind/
  16. lld/
  17. lldb/
  18. llvm/
  19. llvm-libgcc/
  20. mlir/
  21. offload/
  22. openmp/
  23. polly/
  24. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-format-ignore
  29. .clang-tidy
  30. .git-blame-ignore-revs
  31. .gitattributes
  32. .gitignore
  33. .mailmap
  34. CODE_OF_CONDUCT.md
  35. CONTRIBUTING.md
  36. LICENSE.TXT
  37. pyproject.toml
  38. README.md
  39. SECURITY.md
README.md

The LLVM Compiler Infrastructure

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Welcome to the LLVM project!

This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.

C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

Getting the Source Code and Building LLVM

Consult the Getting Started with LLVM page for information on building and running LLVM.

For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.

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