MSTest docs as a submodule

### Describe the issue or suggestion

@gewarren Do you know if that would be somehow possible to have some/most of MSTest docs available in MSTest repo and "cloned"/"submoduled" or whatever solution here so we could make it simpler for us (and copilot) to improve/add documentation as we are adding the new feature?

In the current form, we have to think about all docs to update as we move closer to the release and often time we miss things.

cc @Youssef1313