[clang] [clang][ssaf] Add Entity Linker and associated data structures (PR #181765)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 52623 tests passed
* 963 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### Clang-Unit
<details>
<summary>Clang-Unit.Analysis/Scalable/_/ClangScalableAnalysisTests_exe/EntityLinkerTest/TwoTULinkWithAllCombinations</summary>

```
Script:
--
C:\_work\llvm-project\llvm-project\build\tools\clang\unittests\Analysis\Scalable\.\ClangScalableAnalysisTests.exe --gtest_filter=EntityLinkerTest.TwoTULinkWithAllCombinations
--
C:\_work\llvm-project\llvm-project\clang\unittests\Analysis\Scalable\EntityLinkerTest.cpp:420
Expected equality of these values:
  Entities.at(NameTU1_X_None)
    Which is: 8-byte object <06-00 00-00 00-00 00-00>
  EIdTU1_X_None
    Which is: 8-byte object <00-00 00-00 00-00 00-00>


```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/181765