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/TCPStreamService/TCPSConn.h

@@ -0,0 +1,70 @@
+#ifndef TCPS_CONN_H_
+#define TCPS_CONN_H_
+
+/**
+ * @file TCPSConn.h
+ * @brief One accepted connection of a TCPStreamService (internal).
+ *
+ * Ownership: created by the acceptor thread, then owned and deleted by exactly
+ * one TCPSWorker. `streams` and `closeRequested` are the only fields touched
+ * from other threads; `stream` is guarded by the service topology lock, the
+ * queue by `qMutex`.
+ */
+
+#include "CompilerTypes.h"
+#include "FastPollingMutexSem.h"
+#include "TCPSFrameQueue.h"
+#include "TCPStreamService.h"
+#include "UDPSProtocol.h"
+
+#include <unistd.h>
+
+namespace MARTe {
+
+class TCPSWorker;
+class TCPSServiceStream;
+
+struct TCPSConn {
+    TCPSConn(int socketFd, TCPSWorker *owner, uint32 queueDepth, uint64 handshakeDeadline)
+        : fd(socketFd), worker(owner), subscribed(false), hsHave(0u),
+          hsWant(UDPS_HEADER_SIZE), hsHeaderOk(false), hsDeadline(handshakeDeadline),
+          numStreams(0u), closeRequested(false) {
+        for (uint32 i = 0u; i < TCPS_MAX_CONN_STREAMS; i++) {
+            streams[i] = NULL_PTR(TCPSServiceStream *);
+        }
+        q.Init(queueDepth);
+    }
+    ~TCPSConn() {
+        if (fd >= 0) {
+            (void)close(fd);
+        }
+    }
+
+    int         fd;
+    TCPSWorker *worker;
+
+    /* Worker-thread only. */
+    bool   subscribed;
+    uint8  hs[UDPS_HEADER_SIZE + TCPS_MAX_SUBSCRIBE_PAYLOAD + 1u];
+    uint32 hsHave;
+    uint32 hsWant;
+    bool   hsHeaderOk;
+    uint64 hsDeadline;
+
+    /* Service topology lock. */
+    TCPSServiceStream *streams[TCPS_MAX_CONN_STREAMS]; ///< index = stream index on the wire
+    uint32             numStreams;
+    volatile bool      closeRequested;
+
+    /* qMutex. */
+    FastPollingMutexSem qMutex;
+    TCPSFrameQueue      q;
+
+private:
+    TCPSConn(const TCPSConn &);
+    TCPSConn &operator=(const TCPSConn &);
+};
+
+} // namespace MARTe
+
+#endif // TCPS_CONN_H_