[clang] [clang-format] Add first support for reflection (PR #193794)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

> This thread hasn't been updated since February: https://discourse.llvm.org/t/dedicated-meeting-for-c-26-reflection/88927

This is true, but it doesn't mean that nothing is happening. We continue to meet every two weeks, minutes are available [here](https://docs.google.com/document/d/1xksP-oenhblupguhzM06zN7VH9A-1ydXD5bK3UEsD6Y).

https://github.com/llvm/llvm-project/pull/193794