[WIP] Add tests for the server stability

[wolmir]

https://github.com/iterative/vscode-dvc/issues/2529

Will try a permutation of big changes and files to test that the server side is stable.

• [x] Lots of copies of the same file
• [x] Lots of different file types
• [x] Lots of requests for a single open file
• [ ] Lots of requests for a lot of documents open
• [ ] Lots of workspace changes (delete,move,rename,create)

Then add an e2e smoke test.

Tests are failing, so I'll gradually remove the iterations until we have a baseline for the CI

Then we can have a target to improve, if it's too small

Current Baseline for the tests so far: 100 iterations

I'll add the workspace changes tests and then try again