[clang-tidy] Fix `readability-suspicious-call-argument` crash for arguments...

[clang-tidy] Fix `readability-suspicious-call-argument` crash for arguments without name-like identifier

As originally reported by @steakhal in
http://github.com/llvm/llvm-project/issues/54074, the name extraction logic of
`readability-suspicious-call-argument` crashes if the argument passed to a
function was a function call to a non-trivially named entity (e.g. an operator).

Fixed this crash case by ignoring such constructs and considering them as having
no name.

Reviewed By: aaron.ballman, steakhal

Differential Revision: http://reviews.llvm.org/D120555