[clang] [clang] Adds a RecursiveASTEnterExitVisitor data type (PR #136136)

[via cfe-commits]

Sirraide wrote:

> I’ve actively been working on _removing_ uses of `RecursiveASTVisitor` in favour of `DynamicRecursiveASTVisitor` for a while now because of the former’s rather abysmal impact on both compile-times and binary size

(see #110040, #93462 for more context)

https://github.com/llvm/llvm-project/pull/136136