Don't emit binding pattern pattern / optional parameter error when an initializer is present

[jakebailey]

Fixes #50286

Before #50094, this code was fine because in TS, a question token and an initializer are mutually exclusive.

But after #50094, we now take into account optionality from JSDoc. But that means that we won't have a question token, and therefore can have an initializer, and that initializer can prevent a crash on call. So, we can just skip this error if there's an initializer; in TS code, this won't happen, but it fixes the issue for JS code.

This check is not type-aware. We could be smarter and use the new parameterInitializerContainsUndefined function I added in #52696 to detect undefined (or null, with modification), but there's no point; we already emit a type error beforehand because we will check that the initializer is assignable to the binding pattern and undefined or null are not.

While here, use isOptionalDeclaration instead of checking questionToken and isJSDocOptionalParameter.

[iisaduan]

Looks good!