[clang] Fix quadratic slowdown in AST matcher parent map generation (PR #87824)

[Michael Jabbour via cfe-commits]

michael-jabbour-sonarsource wrote:

Hello,
This seems to cause a noticeable increase in memory consumption on some examples. See https://github.com/llvm/llvm-project/issues/129808#issuecomment-2700015065.

https://github.com/llvm/llvm-project/pull/87824