This PR also shows more completion items when defining a debug config in
a `debug.json` file. Mainly when using a pre build task argument.
### Follow ups
- Add docs for Go, JS, PHP
- Add attach docs
Release Notes:
- debugger beta: Show build task completions when editing a debug.json
configuration with a pre build task
- debugger beta: Add Python and Native Code debug config
[examples](https://zed.dev/docs/debugger)