Fix error handling issues in _remote_debugging module

[pablogsal]

Several error handling patterns in Modules/_remote_debugging/ need cleanup:

• Missing error checks on some code paths (e.g., varint decoding, memory allocation failures)
• Inconsistent error propagation across platforms
• A couple of reference counting issues on error paths

Working on a fix.

Linked PRs

• gh-146308: Fix error handling issues in _remote_debugging module #146309