WIP: DISCUSS - Start LS in background

[d3r3kk]

For #3020

• Just stopping the await in extension might be enough

• We may need some further hook up to defer LS activities cleanly

• Note that there are some extra items that shouldn't merge to master

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)

• Title summarizes what is changing

• Has a news entry file (remember to thank yourself!)

• Unit tests & system/integration tests are added/updated

• Test plan is updated as appropriate

• package-lock.json has been regenerated by running npm install (if dependencies have changed)

[DonJayamanne]

• Unfortunately this won't be enough, we need to propagate this promise all the way up to the extension.
• We need to pass this promise to the isReady of the extension API exposed by us. Just because extension activates doesn't mean the language server has started successfully, hence LS server tests WILL fail if LS is still busy loading.
• Also, delaying this will definitely mess and potentially break Intelli Code. So we need to consider that as well.
• Also, if the activation takes some time, then unit test code lenses and other parts of the code will need to wait fort this to complete, i.e. ensure code that uses language server can still function correctly while LS is still starting in the background.
• Finally, please log the errors use traceError.

[d3r3kk]

Closing to do some further work...