Added timestamping to incoming values and timeout to signal descriptor

Added timestamping to ValueDescriptor to be able to record on a
timebase, timebase uses monotonic_ns() which is a system wide timebase
that can be called by connectors written in a host of languages

Added timeout to signal descriptors, live values now return None when
they are timed out

test/manual/peer.py

@@ -4,7 +4,7 @@ import threading
 from concurrent.futures import CancelledError as FutureCancelledError
 from concurrent.futures import TimeoutError as FutureTimeoutError
 from statistics import mean
-from time import monotonic, perf_counter
+from time import monotonic, monotonic_ns, perf_counter
 from uuid import UUID, uuid4
 
 from rich.logging import RichHandler
@@ -117,8 +117,7 @@ def value_sender_thread(
                 next_send_time += period
 
             value = ValueDescriptor(
-                signal_id=signal_id,
-                value=2.0,
+                signal_id=signal_id, value=2.0, timestamp=monotonic_ns()
             )
 
             message = ValueBatch(
@@ -216,9 +215,7 @@ async def perform_handshake(
         connector_version=CONNECTOR_VERSION.get_version(),
         signals=[
             SignalDescriptor(
-                id=signal_id,
-                name="Dummy signal",
-                type="number",
+                id=signal_id, name="Dummy signal", type="number", timeout_ms=5000
             )
         ],
     )