Add testing panel

[phated]

Problem

We should provide a testing panel (an example seen below) that collects all tests within a project. Users can use this panel to run all or a subset of tests without viewing specific source code.

VSCode provides APIs for this: https://code.visualstudio.com/api/extension-guides/testing
And we can provide a listing of all available tests via a custom LSP message.

Happy Case

A user can use this panel to view all tests in the project. Future work could be to also display proofs configured for the project.

Alternatives Considered

No response

Additional Context

No response

Would you like to submit a PR for this Issue?

Yes

Support Needs

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