Fix: signal/slot macro -> func pointer & network fixes

- convert qt connect calls to use function pointers instead of the signal/slot macros wherever practical (UI classes were mostly left alone, target was tasks and processes)
- give signals an explicit receivers to use the static method over the instance method wherever practical
- ensure networks tasks are using the `errorOccured` signal added in Qt5.15 over the deprecated `error` signal
- ensure all networks tasks have an sslErrors signal connected
- add seemingly missing `MinecraftAccount::authSucceeded` connection for `MSAInteractive` login flow

Signed-off-by: Rachel Powers <508861+Ryex@users.noreply.github.com>

launcher/java/JavaCheckerJob.cpp

@@ -38,7 +38,7 @@ void JavaCheckerJob::executeTask()
     for (auto iter : javacheckers)
     {
         javaresults.append(JavaCheckResult());
-        connect(iter.get(), SIGNAL(checkFinished(JavaCheckResult)), SLOT(partFinished(JavaCheckResult)));
+        connect(iter.get(), &JavaChecker::checkFinished, this, &JavaCheckerJob::partFinished);
         iter->performCheck();
     }
 }