Further json isolation and endpoint implementation

Further isolated json specifics to their own module under protocols/json

Moved global packet classes to their own protocols/packets module

Implemented ConnectorEndpoint and ConnectorRegistry as transport
agnostic connector endpoints for universal connector handling, exposed a
ConnectorRegistry API that will need to be made available to the
JsonServer for it to be able to register and unregister endpoints as it
opens and closes connections

Implemented a top down shutdown architecture where each object is
responsible for its children, this allows for a logical and heirachical
flow, each object has its own stop event, which when its stop method is
called, it sets and then awaits the stopped event to be set by any
worker threads etc, with a mandatory timeout to avoid hanging on
shutdown

src/dynalab_core/constants.py

@@ -2,7 +2,7 @@
 # Copyright (C) 2026 Association Exergie <association.exergie@gmail.com>
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-from dynalab_core.protocols.json.common import VersionDescriptor
+from dynalab_core.protocols.common import VersionDescriptor
 
 
 CORE_VERSION = VersionDescriptor(type="alpha", major=0, minor=0, patch=1)