[clang] [clang-tools-extra] [lldb] [Clang][AST][NFC] (`RecordDecl` -> `CXXRecordDecl`)`::isInjectedClassName` (PR #148195)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

> These files test demangling `RecordDecl::isInjectedClassName`, which will be out-of-date (I think) after merging this PR.

This file uses these symbols as test cases, but they are just examples and aren't coupled to the clang implementation at all, the tests are still valid, even if these were originally constructed from clang as an example.

https://github.com/llvm/llvm-project/pull/148195