ProjectExplorer: Use Core::Id as RunMode "enum values"

This provides a way for third-party plugins to implement run
modes without the need to add a value to the central enum or
using manual workarounds like RunMode(*(int*)&someUniqueObject).

Instead of centrally defined enum values this uses Core::Id that could
be defined anywhere.

Change-Id: Ic350e3d8dbb8042c61b2d4ffec993ca151f53099
Reviewed-by: Daniel Teske <daniel.teske@theqtcompany.com>
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/valgrind/valgrindplugin.h

@@ -34,6 +34,7 @@
 
 #include <extensionsystem/iplugin.h>
 #include <analyzerbase/ianalyzertool.h>
+#include <projectexplorer/projectexplorer.h>
 
 namespace Valgrind {
 namespace Internal {