Before, `KtCodeFragment`/`FirCodeFragment` was analyzed as a part of
its context `KtModule`. This has the following complications:
- In non-source sessions, diagnostic reporting is globally disabled.
For code fragments, however, checking the code before passing it to
the backend is essential.
- Special treatment for call ambiguities in libraries
(`LLLibraryScopeAwareCallConflictResolverFactory`) becomes complicated
as the conflict resolver has to be applied to a library module.
- `KtCodeFragment`s usually have a shorter lifetime than their own
context. Caching may potentially be implemented differently for them.
^KT-61783 Fixed