Bug 1556010 - Use Sqlite window functions to provide better position fixing in...

Bug 1556010 - Use Sqlite window functions to provide better position fixing in reorderChildren. r=Standard8

Tested by toolkit/components/places/tests/bookmarks/test_bookmarks_reorder.js
Note the "parent/sync" annotation and PlacesSyncUtils.order() are no more used,
a bug apart will be filed to remove them.

Differential Revision: https://phabricator.services.mozilla.com/D162270