[clang] Clang AST updates for more details (PR #152372)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

In addition to the comments from @jrtc27, the copyright notices may also be problematic (I commented in the PR on it).

I realize you've got constraints on your end that may make this impractical, but from our end what we'd like to see is:

* The SEI comments should be removed, probably including the copyright notices
* Any existing test code that you've removed needs to be restored; it's fine to modify tests to expect new output (that's normal) but it's generally not okay to remove existing test coverage without justifying why it's safe to remove
* Splitting the PR up into multiple logical changes so it's less massive

https://github.com/llvm/llvm-project/pull/152372