CMakeProcess: Don't use QTimer for checking the canceled state

Create a QFutureWatcher instead and connect to its canceled()
signal.

Replace some includes with forward declarations.

Change-Id: Ie82bf8902ef8c8d87011809bd14b7db3d4f52179
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/cmakeprojectmanager/fileapireader.cpp

@@ -25,6 +25,7 @@
 
 #include "fileapireader.h"
 
+#include "cmakeprocess.h"
 #include "fileapidataextractor.h"
 #include "fileapiparser.h"