Add vscode API DebugSessionOptions

[msujew]

What it does

Closes #8518

Adds the vscode.debug.DebugSessionOptions API to Theia. This enables the following features:

• Show child debug sessions as a tree under the parent sessions (Theia used to show them as siblings)
  • The new compact property will simplify the label and tree structure if possible
• Different debug sessions no longer share the same DebugConsoleSession and therefore are displayed independently
  • Child debug sessions with the consoleMode property set to MergeWithParent will continue to share their console session with each other.
  • You can switch between console sessions with a selector, assuming more than one session is currently running.

The changes to DebugConsoleSession are slightly breaking. While it's still possible to simply inject the DebugConsoleSession directly, its tight coupling to DebugSession makes that impractical. Instead of injecting the DebugConsoleSession directly, a DebugConsoleSessionFactory allows to create a DebugConsoleSession with a provided DebugSession.

How to test

1. Clone this test repo into Theia and make sure the vscode-js-debug extension is installed in Theia.
2. Start a debugging session with the contained Launch Program configuration.
3. Child processes will now be shown as a tree in the threads view.
4. Start a second debugging session with the same configuration
5. Another tree will appear in the threads view and you can switch between the different debug consoles.
6. You can add configuration.consoleMode = undefined; and/or configuration.compact = undefined; after this line, and restart the server to test how these properties influence the debug console/view.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[marcdumais-work]

@paul-marechal @vince-fugnitto Could you help review?

[vince-fugnitto]

The changes look very promising, I only had the chance to quickly review so far and both the code and behavior look correct. I'd like to take some additional time looking more deeply at the code and reviewing additional use-cases.

[vince-fugnitto]

I confirmed that the behavior works as expected:

• confirmed with the test workspace that launching multiple debug sessions works correctly, the threads display nested processes, and the output view contributes a toolbar item to select the different sessions.
• confirmed that normal debug sessions (ex: _'run mocha tests') works as before

[vince-fugnitto]

@msujew I believe if rebased it should fix the CI failures which have been resolved 👍

[vince-fugnitto]

I confirmed last week that the changes work as intended and the behavior is aligned with vscode 👍 The code is also very clean and I have no comments.

I'll let others review if interested :)

[vince-fugnitto]

@paul-marechal @colin-grant-work any additional comments? Else I'll merge the pull-request early this week.

[vince-fugnitto]

@msujew the pull-request just needs to be rebased due to #8706.

[msujew]

@vince-fugnitto Thanks for the heads-up. Rebasing done 👍

[vince-fugnitto]

I'll merge the pull-request tomorrow if there are no objections 👍