core: create qPrefLocationService from SettingsObjectWrapper

Update set/get functions to follow common name scheme:
- get function have same name as in struct prefs
- set function have set_<name>
- signal function have <name>_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/qPrefLocationService.cpp

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "qPrefLocationService.h"
+#include "qPref.h"
+#include "qPrefPrivate.h"
+
+static const QString group = QStringLiteral("LocationService");
+
+qPrefLocationService::qPrefLocationService(QObject *parent) : QObject(parent)
+{
+}
+qPrefLocationService *qPrefLocationService::instance()
+{
+	static qPrefLocationService *self = new qPrefLocationService;
+	return self;
+}
+
+void qPrefLocationService::loadSync(bool doSync)
+{
+	disk_distance_threshold(doSync);
+	disk_time_threshold(doSync);
+}
+
+HANDLE_PREFERENCE_INT(LocationService, "/distance_threshold", distance_threshold);
+
+HANDLE_PREFERENCE_INT(LocationService, "/time_threshold", time_threshold);