Control the lifetime of SshProcessManager

Make it possible to control when the SshProcessManager is
being constructed / destructed. Expose public constructor.

Since different singletons depend on each other, we need
to control the order of creation and destruction of them.

The order of creation is like that:

1. QCoreApplication
2. ProcessReaper
3. ProcessLauncher
4. SshConnectionManager

The order of destruction must be opposite to the above.

Change-Id: Ice07eb751cd61c03cb461816fa1b74ab040a53de
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/app/main.cpp

@@ -32,6 +32,8 @@
 #include <extensionsystem/pluginspec.h>
 #include <qtsingleapplication.h>
 
+#include <ssh/sshconnectionmanager.h>
+
 #include <utils/algorithm.h>
 #include <utils/environment.h>
 #include <utils/fileutils.h>
@@ -538,6 +540,7 @@ int main(int argc, char **argv)
     Utils::ProcessReaper processReaper;
     Utils::LauncherInterface::startLauncher();
     auto cleanup = qScopeGuard([] { Utils::LauncherInterface::stopLauncher(); });
+    QSsh::SshConnectionManager sshConnectionManager;
 
     const QStringList pluginArguments = app.arguments();