[llvm] [clang-tidy] Add performance-move-smart-pointer-contents check. (PR #66139)

[via llvm-commits]

pizzud wrote:

After looking at the various comments (thanks all!) it feels like the consensus was:
- don't suggest fixes (done)
- move shared_ptr out to its own check (done in #67467 )
- be more precise in both language and implementation

Is there a reasonable way to detect expensive moves? Looking for trivially-moveable seems like a decent start, but it's hard to know when a given instance of a type may be large (eg long strings).

https://github.com/llvm/llvm-project/pull/66139