Prevent task execution and debug session creation without workspace trust

[colin-grant-work]

What it does

Fixes #16888
Fixes #16889

Disables debug sessions when a workspace is untrusted.

How to test

1. In an untrusted workspace.
2. Try to run a debug session.
3. You should get a prompt re: trusting the workspace.
4. If you trust the workspace, the session should start; if not, not.
5. You should get a new prompt each time you try to debug. Previously, requesting workspace trust would only produce a prompt once.

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

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