Separate request handling and client communication

[ddoktorski]

• Remove handle_request as method on CairoDebugger
• Update debugger state in handle_request
• Remove send_error method
• Group unsupported request in one arm

[ddoktorski]

This change is part of the following stack:

• Remove main.rs #25
  • Add client connection handling via I/O threads #27
    • Move debugger to separate module #28
      • Make handle_request method of debugger #29
        • Add initialization flow #30
          • Integrate debugger with VM #31
            • Support pause and continue requests #32
              • Add debugger state #38
                • Separate request handling and client communication #39 ◀

_{Change managed by git-spice.}

[piotmag769]

Butiful