[clang-tools-extra] [clang-tidy] Add new check 'misc-scope-reduction' (PR #175429)

[via cfe-commits]

vabridgers wrote:

Thanks for the comments. I'll definitely run on some sample projects to see if the checker works well to consider merging before doing so. 

Are there any objections to me squashing the commits, rebasing and doing a forced push to update? I'll update the commit header with the AI co-pilot info at the same time. 

https://github.com/llvm/llvm-project/pull/175429