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>

Source/Components/Interfaces/UDPStream/UDPSTransportI.h

@@ -0,0 +1,71 @@
+#ifndef UDPS_TRANSPORT_I_H_
+#define UDPS_TRANSPORT_I_H_
+
+/**
+ * @file UDPSTransportI.h
+ * @brief Abstract transport seams used by the UDPStreamer / UDPStreamerClient
+ * DataSources.
+ *
+ * The DataSources only ever touch their transport through these few calls, so
+ * a different transport (TCP) can be plugged in without duplicating the
+ * serialisation, quantisation, publishing and decode logic.
+ */
+
+#include "CompilerTypes.h"
+#include "StructuredDataI.h"
+
+namespace MARTe {
+
+class UDPSClientListener;
+
+/**
+ * @brief Producer-side transport. NOT thread-safe: every call must come from
+ * the owner's sender thread.
+ */
+class UDPSServerI {
+public:
+    virtual ~UDPSServerI() {}
+
+    /** Read the transport configuration. */
+    virtual bool Initialise(StructuredDataI &data) = 0;
+    /** Open sockets and start accepting clients (idempotent). */
+    virtual bool Start() = 0;
+    /** Close everything (idempotent). */
+    virtual bool Stop() = 0;
+    /** Non-blocking housekeeping: accept/evict clients, drain queues. */
+    virtual void ServiceClients() = 0;
+    /** Publish (and cache) a CONFIG payload. */
+    virtual bool SendConfig(const uint8 *payload, uint32 payloadSize) = 0;
+    /** Publish a DATA payload. */
+    virtual bool SendData(uint32 counter, const uint8 *payload, uint32 payloadSize) = 0;
+    /** @return true when at least one client is attached. */
+    virtual bool HasClients() const = 0;
+    /** @return true when the transport uses multicast. */
+    virtual bool IsMulticast() const = 0;
+    /** @return the (bound) port. */
+    virtual uint16 GetPort() const = 0;
+};
+
+/**
+ * @brief Consumer-side transport. Delivers through UDPSClientListener.
+ */
+class UDPSClientI {
+public:
+    virtual ~UDPSClientI() {}
+
+    virtual bool Initialise(StructuredDataI &data) = 0;
+    /** Must be called before Start(). */
+    virtual void SetListener(UDPSClientListener *listener) = 0;
+    virtual bool Start() = 0;
+    virtual bool Stop() = 0;
+    /**
+     * @return Packets missing between the previous DATA packet and the one
+     * being delivered (valid inside OnUDPSData). 0 when the transport does
+     * not track it.
+     */
+    virtual uint32 GetLastDataGap() const { return 0u; }
+};
+
+} // namespace MARTe
+
+#endif // UDPS_TRANSPORT_I_H_