Fix infer callable annotations

[WilliamK112]

Summary

• Share the Python annotation renderer used by stub generation with infer.
• Render top-level function, callable, bound-method, and overload types as valid typing.Callable annotations and add the required import.
• Skip inferred annotations that would require Incomplete, including nested callable types, instead of emitting Pyrefly's internal callable syntax into Python source.
• Add regression coverage for callable parameters, returns, bound methods, and nested callable types.

Fixes #4507

Test Plan

• CARGO_INCREMENTAL=0 CARGO_PROFILE_TEST_DEBUG=0 CARGO_PROFILE_DEV_DEBUG=0 CARGO_BUILD_JOBS=2 cargo test -p pyrefly commands::infer::test::
• CARGO_INCREMENTAL=0 CARGO_PROFILE_TEST_DEBUG=0 CARGO_PROFILE_DEV_DEBUG=0 CARGO_BUILD_JOBS=2 cargo test -p pyrefly stubgen::tests::
• CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 CARGO_PROFILE_TEST_DEBUG=0 CARGO_BUILD_JOBS=2 python3 test.py --no-test --no-tensor-shapes --no-conformance --no-jsonschema
• git diff --check

AI usage

I used an AI coding assistant to help inspect the existing stub-generation implementation, implement the shared renderer, and review edge cases. I manually reviewed the diff and ran all validation listed above.

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D115700626. (Because this pull request was imported automatically, there will not be any future comments.)

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅