[clang-tidy] Ignore cxxRewrittenBinaryOperator in defaulted function decls in modernize-use-nullptr

The check has produced false positives when checking the default implementation of the spaceship operator.
The default implementation should be skipped by the check.

Modified the existing test so that the check runs into the bug without this fix and add another test case.

Fixes #53961.

Patch by Jens Massberg.

Reviewed By: ilya-biryukov

Differential Revision: https://reviews.llvm.org/D138701