VS Code Extension + `DistributedApplicationTestingBuilder`

[afscrome]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

I'd love to see some better integration in the VS Code extension with DistributedApplicationTestingBuilder tests

Describe the solution you'd like

When debugging a test in VS Code, I'd like to be able to

1. View the app host in the App Host's window
2. See the code lens highlights of custom resources

This would really help to compensate for the lack of dashboard - e.g. being able to see the current state of the resource, seeign what ports a resource is using etc.

Additional context

I can see in the logs that the back channel started so I'd hope we'd be able to connect.

[afscrome]

Thinking about #15576 some more, I wonder if there will be a chicken and egg problem here - if the app host process is broken on a breakpoint, then the backchannel won't be able to respond.

Although the data would still be useful when running tests but wanting to see progress without breaking on the debugger. (e.g. a WaitForResourceHealthyAsync() on a resource that doesn't go healthy).

[adamint]

I think we may want to support dashboard launch inside of tests instead
cc @mitchdenny