Fix TSP inferred returns for definition-site computed types

[WilliamK112]

Fixes #4042.

Summary

• Treat exact TSP range requests for function and method definition names like identifier lookups instead of expression traces.
• Preserve declaration-based computed types so unannotated functions, methods, and property getters keep their inferred returnType at definition sites.
• Add TSP interaction coverage for definition-site ranges plus a same-name reference range under untyped-def-behavior = check-and-infer-return-type.

Validation

• cargo +stable-x86_64-pc-windows-gnu test -p pyrefly test_get_computed_type_definition_site_uses_inferred_return_type -- --nocapture
• cargo +stable-x86_64-pc-windows-gnu test -p pyrefly get_type_queries
• cargo +stable-x86_64-pc-windows-gnu test -p pyrefly tsp_interaction
• cargo +stable-x86_64-pc-windows-gnu fmt --all --check
• git diff --check
• cargo +stable-x86_64-pc-windows-gnu test -p pyrefly test_shape_dsl_reports_multiple_errors -- --nocapture

I also attempted the full cargo +stable-x86_64-pc-windows-gnu test -p pyrefly suite. It reached 6188 passed, 1 failed; the only failure was the unrelated test::shape_dsl::test_shape_dsl_reports_multiple_errors internal watchdog timeout (Error: Test took too long (> 20s)) during the full parallel run. The same test passed when rerun directly, as shown above.