[clang] [Clang] Implement Wpointer-bool-conversion-strict (PR #131523)

[Erich Keane via cfe-commits]

erichkeane wrote:

I can't for the life of me see a good way to use this.  The `if(p)` pattern is so common that no code base could ever turn on this warning.  We could PERHAPS check that we're in the process of checking a condition expression and suppress this diagnostic, or recognize this pattern somehow, but without some more work to make this more useful, I don't think we can accept this diagnostic.

https://github.com/llvm/llvm-project/pull/131523