After this PR we can run all the in-tree launch.json examples from [this
repo](https://github.com/microsoft/vscode-recipes).

Things done:

- Fill in default cwd at a lower level for all adapters
- Update launch.json parsing for DebugScenario changes
- Imitate how VS Code normalizes the `type` field for JS debug tasks
- Make version field optional
- Extend the variable replacer a bit

Release Notes:

- Debugger Beta: fixed issues preventing loading and running of debug
tasks from VS Code's launch.json.

---------

Co-authored-by: Anthony Eid <hello@anthonyeid.me>
Co-authored-by: Anthony <anthony@zed.dev>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>