Add brew debugger command

[Rylan12]

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This PR creates a new dev command called brew debugger which spawns a debugger for Homebrew commands. To use the debugger, add a method call to binding.break anywhere in the code. Then, run brew debugger <cmd> (this supports passing flags to the command by doing brew debugger -- <cmd> --flags). This will automatically spawn a debugger session at the breakpoint using rdbg and the debugger gem.

I've also added a VS Code launch configuration to attach to an existing debug session. If you're using VS Code, you can run brew debugger --open <cmd>. Then, use the Run and Debug tab of VS Code to attach to the debugger to use the VS Code debugging frontend. I'm happy to provide a video showing this if my description is confusing.

Ultimately, my goal is to allow you to add breakpoints in VS Code and just run directly from there avoiding the need to create a session using brew debugger, but that's going to take some more work. I'm not sure the rdbg VS Code extension will support that super cleanly at the moment, so I might need to add some more hack-y workarounds to do that. If anyone has any insight, feel free to let me know.

CC @issyl0 and @krehel because we talked about this today on the maintainer zoom

[MikeMcQuaid]

Looking good, thanks @Rylan12! A few comments but can always merge as-is and iterate.