Implement Cast Streaming mirroring, DLNA casting, daemon+GUI, and breadd integration

Builds out the full v1 scope: a vendored+patched openscreen subset for
low-latency Cast Streaming (Mirroring receiver 0F5096E8) alongside the
existing Cast V2/HLS and new DLNA/AVTransport casting paths, breadcastd's
Idle/Casting state machine with a private IPC socket, the breadcast GTK4
popup as a thin IPC client, and bread.cast.*/bread.command.cast.* breadd
integration (device discovery, start/stop, mirroring lifecycle events).
Also adds bakery/systemd/Forgejo CI packaging.

Validated end-to-end against a real Chromecast/Google TV: negotiated
Cast Streaming session, live pipeline playback, and daemon+GUI click-to-cast/
stop through the actual popup.

breadcast-caststream-sys/vendor/openscreen/platform/api/trace_event.h

@@ -0,0 +1,75 @@
+// Copyright 2022 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PLATFORM_API_TRACE_EVENT_H_
+#define PLATFORM_API_TRACE_EVENT_H_
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "platform/api/time.h"
+#include "platform/base/error.h"
+#include "platform/base/trace_logging_activation.h"
+#include "platform/base/trace_logging_types.h"
+
+namespace openscreen {
+
+// A collection of common properties of trace events.
+struct TraceEvent {
+  // Constructor with only the required fields.
+  TraceEvent(TraceCategory category,
+             Clock::time_point start_time,
+             const char* name,
+             const char* file_name,
+             uint32_t line_number);
+
+  TraceEvent();
+  TraceEvent(TraceEvent&&) noexcept;
+  TraceEvent(const TraceEvent&);
+  TraceEvent& operator=(TraceEvent&&);
+  TraceEvent& operator=(const TraceEvent&);
+  ~TraceEvent();
+
+  std::string ToString() const;
+
+  // May be called to truncate all std::strings on this object.
+  static const size_t kMaxStringLength = 1024;
+  void TruncateStrings();
+
+  // The category of this event.
+  TraceCategory category;
+
+  // Timestamp for when the event was created.
+  Clock::time_point start_time;
+
+  // Name of this operation.
+  const char* name = nullptr;
+
+  // Name of the file the log was generated in.
+  const char* file_name = nullptr;
+
+  // Line number the log was generated on.
+  uint32_t line_number = 0;
+
+  // The trace ids of this event and its ancestors.
+  TraceIdHierarchy ids;
+
+  // Flow IDs associated with this event.
+  std::vector<uint64_t> flow_ids;
+
+  // Optional result of the trace event.
+  Error::Code result = Error::Code::kNone;
+
+  // Optional list of arguments. May contain 0, 1, or 2 arguments.
+  // Excess arguments will remain unused.
+  using Argument = std::pair<const char*, std::string>;
+  std::vector<Argument> arguments;
+};
+
+std::ostream& operator<<(std::ostream& out, const TraceEvent& event);
+
+}  // namespace openscreen
+
+#endif  // PLATFORM_API_TRACE_EVENT_H_