[clang] [clang][test] add testing for the AST matcher reference (PR #110258)

[Julian Schmidt via cfe-commits]

5chmidti wrote:

This is an attempt to reland this PR, which created buildbot failures because of the python version not supporting subscripted types, and because previously, the test generation script would try to compile the code with a `clang` from `PATH`.

Removed the type-hints that didn't work, and testing that the examples work has been removed from the test generation script. That part will also be tested when running the unit test, and was only added to catch compile failures of the examples earlier.

https://github.com/llvm/llvm-project/pull/110258