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/minecraft/WorldList.cpp

@@ -53,8 +53,7 @@ WorldList::WorldList(const QString &dir)
     m_dir.setSorting(QDir::Name | QDir::IgnoreCase | QDir::LocaleAware);
     m_watcher = new QFileSystemWatcher(this);
     is_watching = false;
-    connect(m_watcher, SIGNAL(directoryChanged(QString)), this,
-            SLOT(directoryChanged(QString)));
+    connect(m_watcher, &QFileSystemWatcher::directoryChanged, this, &WorldList::directoryChanged);
 }
 
 void WorldList::startWatching()