feat(tcp): TCPStreamer DataSources, in-process TCPStreamService, stream multiplexing and TCPStreamJoin

Add TCPStreamer/TCPStreamerClient (TCP transport behind the UDPSServerI/UDPSClientI
seam), an optional single in-process TCPStreamService serving many streams over
worker threads, multiplexed SUBSCRIBE (comma list, stream index in fragmentIdx),
and TCPStreamJoin, which merges several streams into one sample-and-hold stream
paced by a master. StreamHub takes a comma list of streams over one connection.
Includes GTests, E2E scenarios s58-s73 and docs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Test/E2E/suite/tests_py.py

@@ -68,7 +68,8 @@ class TestScenarios(unittest.TestCase):
         self.assertIn("direct", kinds)
         self.assertIn("recorder", kinds)
         direct_ids = {s["id"] for s in S.SCENARIOS if s["kind"] == "direct"}
-        self.assertEqual(direct_ids, {"s52_direct_unicast", "s53_direct_multicast"})
+        self.assertEqual(direct_ids, {"s52_direct_unicast", "s53_direct_multicast",
+                                    "s58_direct_tcp", "s59_direct_tcp_service"})
         recorder_ids = {s["id"] for s in S.SCENARIOS if s["kind"] == "recorder"}
         self.assertEqual(recorder_ids, {"s54_recorder"})