[clang] [NFC][analyzer] Cleanup checker calls in `ExprEngine::ProcessStmt`, `ExprEngine::Visit*` (PR #218691)

[Gábor Tóthvári via cfe-commits]

tigbr wrote:

I think those `return` statements still act as `break` statements between the cases to avoid fall through.

https://github.com/llvm/llvm-project/pull/218691