Connection status client and gui can get out of sync.

**Describe the bug**

There are several occasions where Client connection and GUI can get out of sync.
If this is the case the gui will show connected state (and disconnect button) while still connected or the gui will show disconnected state (and connect button) while not connected.
Also there are cases where GUI shows the "Disconnect" button, but opens the "Connect" dialog when pressed.

**To Reproduce**

This mostly happens when you change to an invalid device while connected.
It also happens in other cases of device errors but these are harder to reproduce.

**Expected behavior**

GUI should always show the correct state.

**Screenshots**

**Operating system**

**Version of Jamulus**
All Jamulus versions

**Additional context**

I finally found the problem (after a long time), And there are two causes:
1: Connect/Disconnect is implemented in the CClientDlg code, with a lot of calls to CClient (Doesn't belong here, since this is not GUI functionality.)
2: Some functions in CCLient have ambiguous names, so wrong functions are used to check if connected (actually checking Sound.IsStarted)

This issue will be solved in my "sound re-design" repo.

Start by tracing connection and disconnect handling between CClientDlg and CClient, focusing on invalid-device and other device-error paths. Verify which connection checks drive the GUI state and buttons; done means the GUI consistently reflects the actual connection and opens the correct connect or disconnect action. The issue notes that work has moved to a sound re-design repo.

Written by the indexing model from the issue text.