Rewrite GDB server in Python

[mrexodia]

The upstream udbserver dependency was not working correctly (missing packets, no proper stop reasons etc), so I had the clanker (gpt-5.6-sol) rewrite it completely in Python.

[gemini-code-assist]

Code Review

This pull request introduces a GDB compatibility proxy (GdbCompatibilityProxy) to provide Windows process metadata (such as loaded PE images, thread info, and TEB address) to Unicorn's GDB server, enabling better integration with debuggers like IDA Pro. The review feedback highlights several areas for improvement, including correcting the RSP packet size calculation to account for framing overhead, preventing proxy execution if stopped during connection retries, properly closing the DefaultSelector to avoid resource leaks, addressing compatibility risks with the hardcoded qSupported response, and updating test assertions to validate the full packet length.

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