[clang-tools-extra] [analyzer] Split alpha core Identical Expression tests (PR #119543)

[Julian Schmidt via cfe-commits]

https://github.com/5chmidti commented:

Please change the `RUN` lines to use `check_clang_tidy` like so:
`// RUN: %check_clang_tidy %s bugprone-branch-clone %t`, and drop the `BUGPRONEBRANCH` suffix in `bugprone-branch-clone.cpp`, as it is redundant after this change, and after removing the accidental copies of `-IDENTEXPR`s.

Because the other test already had the suffix, I'd just keep it. You can add a suffix to `check_clang_tidy` via `-check-suffixes=IDENTEXPR`

https://github.com/llvm/llvm-project/pull/119543