VS Code's Disposable returns `any` and for #6085 we need to properly handle async disposables, which means having better typing.
+ change `any` use in dispose methods

Instead of terminating after 100ms, allow 3s for server shutdown. Also change `disposeAll()` from fire-and-forgetting everything, to instead wait up to 3s for them to complete.
This will ensure that during extension shutdown, we block the deactivate method for at least 3s to allow things to shut down.
Doing this required splitting sync/async disposables so we can await disposing things like the analyzer. This also meant avoiding the VS Code Disposable interface because it returns `any` so we can have some safety where we have async disposables.
Fixes #6085