Support seamless integration with ruby/debug

[st0012]

Summary

This PR enhances the debugging experience by keeping users within the IRB session when executing debugging commands. This ensures users retain multi-line input support and access to all IRB commands, while benefiting from debug's enhanced debugging functionalities.

Simply put: this will be pry-byebug equivalent for IRB and debug.

Demonstrations

Current Debugging Experience:

Current.debug.integration.mp4

Improved Debugging Experience:

Improved.debug.integration.mp4

Design & Implementation

• Debugging commands execution is handled by ExtendCommand::Debug#execute, which performs several actions:

  1. Checks if the debugging command originates from a binding.irb call.
  2. Sets up the debug gem if the above condition is met.
  3. Inserts a debug breakpoint at Irb#debug_break with the intended command.
  4. Exits the current Irb#run call via throw :IRB_EXIT.

  When Irb#debug_break is automatically called after step iv, the breakpoint triggers, executing the intended command.

• The new IRB::Debug::UI class and Irb#debug_readline method transform IRB into the debugger session's UI. Depending on the user's input, the behavior varies:

  1. Debugging commands (e.g., step 3) are passed directly to the debugger.
  2. IRB commands (e.g., show_source Foo#bar) are evaluated within the IRB session.
  3. Other inputs (e.g., my_object.my_method) are passed to the debugger.

  After the debugger evaluates the input, it calls Irb#debug_readline again, maintaining the impression of a continuous IRB session.

Known Limitations

• Local variables assigned in the original IRB session are not accessible in the irb:rdbg session.
• The _ variable is not functional until debug supports it.

Resolves #521

[st0012]

@tompng would you mind giving it another look when have time? Thx 🙏

[tompng]

LGTM 👍
IRB is completely a great debugger now 🎉