Replace static_casts by QOverload where possible

Mainly to get rid of the QProcess::finished deprecation warning.

Also adjust coding style in the surrounding connects when needed.

Change-Id: I12f9b248c7974b892c4a069356e578e80f8c59e9
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/perforce/perforcechecker.cpp

@@ -42,7 +42,7 @@ namespace Internal {
 PerforceChecker::PerforceChecker(QObject *parent) : QObject(parent)
 {
     connect(&m_process, &QProcess::errorOccurred, this, &PerforceChecker::slotError);
-    connect(&m_process, static_cast<void (QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished),
+    connect(&m_process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
             this, &PerforceChecker::slotFinished);
 }