[DWDS] Make pause a no-op on WebSocketProxyService

[srujzs]

We can't actually pause during execution so we shouldn't signal that we did.

[srujzs]

I tried removing _currentPauseEvent entirely, but it looks like Flutter tools' testing is relying on a pause event at start, specifically from here when the isolate is created and pauseIsolatesOnStart is true. For now, I left that, modifications to that flag which also results in a new pause event being sent, and resume, where a resume event is sent.

It's not clear to me whether PauseStart and Resume should still be sent even though we don't pause. I suppose it signals on start that the isolate has started but we haven't run main yet?