[clang] [clang-tools-extra] [clang] Unify `SourceLocation` and `IdentifierInfo*` pair-like data structures to `IdentifierLoc` (PR #135808)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-gcc-ubuntu` running on `sie-linux-worker3` while building `clang-tools-extra,clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/174/builds/16282

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
PASS: lit :: shtest-not.py (90224 of 90234)
PASS: lit :: allow-retries.py (90225 of 90234)
PASS: lit :: discovery.py (90226 of 90234)
PASS: lit :: shtest-external-shell-kill.py (90227 of 90234)
PASS: lit :: googletest-timeout.py (90228 of 90234)
PASS: lit :: selecting.py (90229 of 90234)
PASS: lit :: shtest-timeout.py (90230 of 90234)
PASS: lit :: max-time.py (90231 of 90234)
PASS: lit :: shtest-shell.py (90232 of 90234)
PASS: lit :: shtest-define.py (90233 of 90234)
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1853.103678

```

</details>

https://github.com/llvm/llvm-project/pull/135808