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/libs/utils/completingtextedit.cpp

@@ -114,7 +114,7 @@ void CompletingTextEdit::setCompleter(QCompleter *c)
 
     completer()->setWidget(this);
     completer()->setCompletionMode(QCompleter::PopupCompletion);
-    connect(completer(), static_cast<void (QCompleter::*)(const QString &)>(&QCompleter::activated),
+    connect(completer(), QOverload<const QString &>::of(&QCompleter::activated),
             this, [this](const QString &str) { d->insertCompletion(str); });
 }