[clang] [clang-tools-extra] [analyzer] Remove alpha.core.IdenticalExpr Checker (PR #114715)

[Julian Schmidt via cfe-commits]

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5chmidti wrote:

Thanks for changing these to be more understandable w.r.t. what has changed. Could you please do a follow-up PR that splits this file, so we have the diff that shows no capabilities were lost in this PR/commit, and then have the tests be where the checks are (e.g., `misc/redundant-expression-csa-identicalexpr.cpp`?)

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FYI: When merging with the other tests in a follow-up, note that clang-tidy has a test-driver for lit, e.g., 
- `// RUN: %check_clang_tidy %s -check-suffixes=,DEFAULT cppcoreguidelines-avoid-non-const-global-variables %t` for `CHECK-MESSAGES` and `CHECK-MESSAGES-DEFAULT`
- `// RUN: %check_clang_tidy %s cppcoreguidelines-avoid-non-const-global-variables %t` for `CHECK-MESSAGES`

https://github.com/llvm/llvm-project/pull/114715