[clang] [clang][analyzer] Remove checker 'alpha.core.CastSize' (PR #156350)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat approved this pull request.

I support the removal of this checker, because it implements a heuristic that finds and reports a very specific bug which is (as far as I see) not a "natural" mistake that would appear during real-world development.

https://github.com/llvm/llvm-project/pull/156350