Remove muxConnectionManager and replace with MuxManager

[temporal-nick]

What was changed

• Replaced muxConnectionManager with MuxManager in transport.go
• Allowed passing in a context to WithConnection, threads blocked there will correctly observe configured timeouts
• New goroutine will wake all threads waiting in WithConnection every 5 seconds to check on their timeouts. This represents no change in lock correctness relative to the existing Broadcast behavior. (e.g. there was already an unlocked section in between waiting threads and the checked condition, and the condition is still checked.)
• Fine-tuned lifecycle management for more reliable unit tests
  • MuxManagers are now created with New -> Configured -> Started. The MuxManager's MuxProvider keeps track of whether it has been started and whether it has been fully cleaned up. Waiting on CleanupCh from the appropriate component allows goroutines to block until all resources have been closed.

Why?

Replacing the muxConnectionManager will remove its current locking bugs and replace it with this better-behaved pattern.

In adapting the existing unit tests, several bugs were found and fixed, and the observability has been improved.

• Session.Ping() is now exposed from the MuxManager for easy re-use. Ping() on a dead session will immediately close the channel, removing the need to wait in unit tests.
• All components now expose a cleanup channel, which removes the need to time.Sleep in unit tests

[pglass]

nit: What do you think about calling this WithConnectionOrElse?

[temporal-nick]

I could go either way on this. Usually Try is the thing that tells you the method won't block, but I agree that OrElse does basically the same job in this case

[pglass]

Do we need this, since we have the goroutine waiting on shouldShutdown already?

	go func() {
		<-shouldShutDown.Channel()
		err := listener.Close()
		if err != nil {
			logger.Fatal("listener.Close failed", tag.Error(err))
		}
		connPv.hasCleanedUp.Shutdown()
	}()

I guess we could Accept() and then another goroutine could toggle shouldShouldDown to at L80. But if that's a concern, it could be toggled true at L89, also.

[temporal-nick]

The listener would be cancelled regardless. This just customizes the error message

[pglass]

nit: remove comment