Move ClipboardImageModelFactory ownership to feature controller.

Previously the ClipboardImageModelFactory was owned by the user session
initializer. Now, it will be owned by the ClipboardHistoryController.
This better aligns its lifecycle with clipboard history feature code
and removes one-off feature object ownership from the user session
initializer.

Bug: b:301264185
Change-Id: Ib518d4da2316b48f217b83f2a23e3a1b5f94205f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4884013
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/main@{#1199944}