Frontend(-GNOME): revert ChatViewSyncManager's state machine

The state machine has a corner case bug with the synchronization between
QueueAdd() and QueueSync(). Sync can be executed before the Added/ReadyToSync
state has been reached. The frontend is probably triggering this race condition
and should be avoided if possible. If it can't be avoided then the state machine
based sync manager needs to deal with this like the old sync manager did.

Revert "Frontend: fixed Trace.Call() calls in ChatViewSyncManager"
Revert "Frontend: enhanced exception messages of state machine"
Revert "Frontend: removed unreachable code from State.ctor()"
Revert "Frontend: fixed SyncInfo.SyncRoot being never initialized"
Revert "Frontend: fixed logger calls"
Revert "Frontend: updated copyright info"
Revert "Frontend: coding standards fixes"
Revert "Frontend: stop using Activator.CreateInstance()"
Revert "Frontend: make ChatViewSyncManager.SetState() internal"
Revert "Frontend: avoid logic in State ctors"
Revert "Frontend: catch all exceptions in thread pool workers to prevent AppDomain shutdowns"
Revert "Frontend: fixed leaking ChatViewSyncManager.Chats"
Revert "Frontend: moved private methods into worker dispatch context as they won't be reused"
Revert "Frontend: /rejoin didn't work with ChatViewSyncManager due calling Sync while already synced"
Revert "Frontend(-GNOME): ChatViewSyncManager's internals refactored into a state-machine"

This reverts commit 1495be27eece4456ef4e340228b169bd2e199e34.
This reverts commit a204e6f9f5c6c6b33b4962c01bdcd006d9dd941b.
This reverts commit b44ee256eb6687561bb0e1163cbdd3499c84e772.
This reverts commit 0f999e6ae60869d66cf9c833c6faa96f52ff4028.
This reverts commit 863f0a069652a66936912e8038b7551e84d91596.
This reverts commit 64bb18419503c80087748ff4d3f1f2da0406c8dd.
This reverts commit 3cedf73c6564c9613daf486e060ffecaab535d14.
This reverts commit d626bf9f8227e68c5c7a216e4bdb476efb8b0597.
This reverts commit 36b23ae0bbcf9b953cf538c86ccf73b31e44fcde.
This reverts commit 5bd7b2ecb8b12ac30525cb8d4a9ac3350e996bf1.
This reverts commit a5e8d5030d983f08e4a8eb55748c9c198fb7ba08.
This reverts commit dce4f7b57efb6ca82d63d740d2879bf1f9582c73.
This reverts commit eadcf35d829cf7610a4c31613f1c9e7b202789ae.
This reverts commit ccd8981b3cb830eaba446f48425c6c8c35c402ab.
This reverts commit cfddd43d9c096f56e62a5ca9947d6223beccd97d.