Add test cases to `oxc_semantic` that check scope flag behavior.
Also contains these tweaks:
- fix: allow disabling `with_module` on `SourceType`
- refactor: move `SymbolTester` to a separate file
- chore: add `Expect` trait & implement it on `SymbolTester`
A test harness for checking results of semantic analysis.
I got tired of writing ad-hoc test cases when finding bugs in semantic
analysis, so I made this.