[clang-tools-extra] [clang-tidy] support query based custom check (PR #131804)

[Congcong Cai via cfe-commits]

HerrCai0907 wrote:

> Main reason is simple, easy to modify check and add new check in subconfigs.

It is also support to add new check in subconfigs, to modify check is thing I did not implement yet. (There are FIXME in merge config part of code)
In theory, these two configurations are equivalent. I think flattening the configuration items will only reduce readability, because we cannot define a YAML schema for it.

https://github.com/llvm/llvm-project/pull/131804