[clang-tidy] Improve `google-explicit-constructor` checks handling of `explicit(bool)` (#82689)

We now treat `explicit(false)` the same way we treat `noexcept(false)`
in the noexcept checks, which is ignoring it.

Also introduced a new warning message if a constructor has an `explicit`
declaration which evaluates to false and no longer emit a faulty FixIt.

Fixes #81121