core: copy Animations from SettingsObjectWrapper to qPref as its own class

Update set/get functions to follow common name scheme:
- get function have same name as in struct preferences
- set function have set_<name in struct preferences>
- signal function have <name in struct preferences>_changed

one class one .h/.cpp is the C++ idiom. Having load/sync of each
variable in 1 functions (in contrast to the distributed way SettingsObjectWrapper
handles it) secures the same storage name is used. Having the set/get/load/sync
functions grouped together makes it easier to get an overview.

REMARK: this commit only defines the class, it is not active in production
Signed-off-by: Jan Iversen <jani@apache.org>

core/settings/qPrefAnimations.cpp

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "qPref.h"
+#include "qPref_private.h"
+#include "qPrefAnimations.h"
+
+qPrefAnimations::qPrefAnimations(QObject *parent) : QObject(parent)
+{
+}
+qPrefAnimations *qPrefAnimations::instance()
+{
+	static qPrefAnimations *self = new qPrefAnimations;
+	return self;
+}
+
+void qPrefAnimations::loadSync(bool doSync)
+{
+	disk_animation_speed(doSync);
+}
+
+HANDLE_PREFERENCE_INT(Animations, "/animation_speed", animation_speed);