[Launcher Sort] Temporary sort - part 4

This CL does the following things:

(1) Add one extra parameter to `RequestMoveItemToFolder()` to represent
the reason of moving an item into a folder.

(2) When two items are merged and the app list is under temporary sort,
the sort order is cleared while the item local positions are committed.

Bug: 1260447
Change-Id: I75c4caf37741577e142070d9a768f13e5fd826bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3262407
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Reviewed-by: Toni Barzic <tbarzic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#940745}