Added origin descriptor to SignalDescriptor and adapted connector registry for loopback connector redesign

SignalDescriptor now have a new origin field to distinguish "source"
from "derived" signals, this is ahead of the internal loopback system
for data processing, all external conectors must use source, derived is
targeted only for internal use

The connector registry has been adapted to now have a unique internal
loopback, this does not have an associated endpoint so it is stored
apart and all relevant functions have been updated to include it for
proper handling of signals by DLPak etc

test/manual/peer.py

@@ -119,7 +119,9 @@ def value_sender_thread(
             message = ValueBatch(values=[])
             for i in range(10):
                 value = ValueDescriptor(
-                    signal_id=signal_id, value=2.0, timestamp=monotonic_ns()
+                    signal_id=signal_id,
+                    value=2.0,
+                    timestamp=monotonic_ns(),
                 )
                 message.values.append(value)