[clang-tools-extra] [NFC][clang-tidy]improve performance for misc-unused-using-decls check (PR #78231)

[Congcong Cai via cfe-commits]

HerrCai0907 wrote:

> LGTM. There is open issue for performance of this check. Consider mentioning this in release notes as some generic performance improvement.

I have also seen this issue. But after optimization, this check is still slow. I guess registering too many pattern causes performance issue but I cannot find a good solution to optimize it.

https://github.com/llvm/llvm-project/pull/78231