Improve VS Code debugger support

[Rylan12]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

Follow-up to #18050

This PR improves the VS Code launch configuration to work with brew debugger to allow you to launch debug sessions directly from VS Code. It also allows you to use the built-in breakpoints feature without needing to manually add binding.break.

Now, you can choose "Debug Homebrew command" in the VS Code debug tab. This will prompt you to specify a brew debugger command to run, defaulting to the basename without extension of the currently open file (to make it easy to debug a certain command if you have its file open). You can change the command and add flags as necessary, and it should remember the last choice that you made with any particular active file.

The PR adds an rdbg shim which just calls the correct rdbg executable with HOMEBREW_RDBG set. Setting this variable tells bin/brew that it's okay to pass RUBY_DEBUG_* configuration variables to the filtered environment (as this is the easiest way to use the existing rdbg VS Code extension).

Finally, I removed the --stop option from brew debugger as I think it just makes sense to have as the default. If there is a location closer to startup that would be useful to debug from, just add a breakpoint using either of the methods. I'm totally open to reverting this part, though, if people would find that useful.

[MikeMcQuaid]

This is great, nice work @Rylan12!