* initial wip in the extension host

* wip

* wip

* wip

* continued progress

* update api from discussion

* update for new proposal

* wip

* update to lastest testing api, almost everything working

Refs https://github.com/microsoft/vscode/issues/115089
Design https://gist.github.com/connor4312/73f1883d720654834b7fd40550d3b6e0

* re-wire retirement state

* update actions to new async test structure

* minor cleanup

* remove unused es2018 that failed build

The WorkspaceTestCollectionService duplicated collection logic
unnecessarily. Centralize to the TestService's collection.

This also moves the state updates for discovering tests, and a new
update for adding roots, into the diff, which lets us synchronize those
changes with the changes to test collections.

There's a super crazy bug with the "run all" action that I have
not dove into yet.