Utils: Move ProcessArgs class into filepair of its own

There's not much interaction between ProcessArgs and QtcProcess
and both .cpp are still quite big, with non-trivial bits.

Change-Id: Id84202f6c34057bf87cc8f27fbb45f78f105e9a5
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/macroexpander.cpp

@@ -26,8 +26,9 @@
 #include "macroexpander.h"
 
 #include "algorithm.h"
+#include "fileutils.h"
+#include "processargs.h"
 #include "qtcassert.h"
-#include "qtcprocess.h"
 #include "stringutils.h"
 
 #include <QCoreApplication>