[Companion][Simulator] Add custom qDebug message handler/formatter (#4475)

* [Companion][Simulator] Add custom qDebug message handler/formatter as an option. Keeps support for QT_MESSAGE_PATTERN env. var.

* [Simulator] Show system messages of level qInfo and above in debug console.

* [Simulator] Still capture screenshot to clipboard if path is not accessible (and screenshot results now print to simulator debug console).

* Fix for older CMake.

* [Companion] Do not start debug message handler if app is shutting down, and add null checks before using it; Increase backtrace report depth; Add OTx headers; Add Companion exit status debug; Clean up unused code.

* [Simulator] Add asynchronous FIFO buffer for handling debug output/display more efficiently. (#4488)
(cherry-picked from b12bd7d7be)

companion/src/simulation/debugoutput.cpp

@@ -21,6 +21,7 @@
 #include "debugoutput.h"
 #include "ui_debugoutput.h"
 
+#include "appdebugmessagehandler.h"
 #include "appdata.h"
 #include "filteredtextbuffer.h"
 
@@ -100,6 +101,9 @@ DebugOutput::DebugOutput(QWidget * parent, SimulatorInterface *simulator):
   connect(ui->actionToggleFilter, &QAction::toggled, this, &DebugOutput::onFilterToggled);
   connect(ui->filterText, &QComboBox::currentTextChanged, this, &DebugOutput::onFilterTextChanged);
 
+  if (AppDebugMessageHandler::instance())
+    connect(AppDebugMessageHandler::instance(), &AppDebugMessageHandler::messageOutput, this, &DebugOutput::onAppDebugMessage);
+
   // send firmware TRACE events to our data collector
   m_simulator->installTraceHook(firmwareTraceCb);
 }
@@ -108,6 +112,8 @@ DebugOutput::~DebugOutput()
 {
   saveState();
 
+  if (AppDebugMessageHandler::instance())
+    disconnect(AppDebugMessageHandler::instance(), 0, this, 0);
 
   if (m_dataBufferDevice) {
     disconnect(m_dataBufferDevice, 0, this, 0);
@@ -198,6 +204,14 @@ void DebugOutput::onDataBufferOverflow(const qint64 len)
   }
 }
 
+void DebugOutput::onAppDebugMessage(quint8 level, const QString & msg, const QMessageLogContext & context)
+{
+  if (level > 0) {
+    firmwareTraceCb(qPrintable(msg));
+    firmwareTraceCb("\n");
+  }
+}
+
 /*
  * UI handlers
  */