[clang] [Webkit Checkers] Introduce a Webkit checker for memory unsafe casts (PR #114606)

[Devin Coughlin via cfe-commits]

devincoughlin wrote:

Thanks Rashmi! I suggest pulling the minor ASTMatcher infrastructure improvements for Objective-C into a separate PR and merging that first, separately from the new checker. For the ASTMatcher work, @AaronBallman is a good person to review.

https://github.com/llvm/llvm-project/pull/114606