Partial Semantic Mode Meta-Issue #39035

See #37713 as a pre-requisite for this issue!

#38561 implements the core idea proposed in #37713.

Beyond that, there is still a set of UX issues that we should probably address:

• make cross-file go-to-definition work in the syntax-only server (Make cross-file go-to-definition work in the syntax-only server #39037)
• make find-all-refs work on unresolved locals (Ensure find-all-refs works on unresolved locals #38836)
• better display experience for error types on the syntax server (Provide a better display experience for unresolved values and types #39032)
• expand when isNewIdentifierLocation on the syntax server (Expand when isNewIdentifierLocation is set in the syntax server #39033)
• consider loose completions on the syntax server on unresolved/error types (Consider loose completions in the syntax server on unresolved/error types #39034)