[analysis_server] Switch LSP tests to use workspaceAnalysisComplete() instead of progress/status notifications

Progress/status notifications for analysis are not a reliably indicator of analysis being complete. They might not be sent if there is no work, or may have multiple bursts in case of plugins. The new `dart/workspace/analysis/complete` request was added as a reliably signal that all pending work is complete.

This change updates all tests that used the progress/status notifications to know analysis had completed (except tests that were specifically testing the notifications), removing concepts like "initialAnalysis" which could be unsound with plugins (or debouncing of status notifications).

I also replaced some `await pumpEventQueue();` which followed calls to the server with `await workspaceAnalysisComplete();` because it should also be more reliable. However `pumpEventQueue` remains when it's after synchronous modifications to the resource provider, since otherwise the server might not have started processing the watch event before we called it.

Change-Id: I342890c82e18848b9bffc00876141216fbbcd5c7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/526482
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>