Get rid of remaining WebUIDataSource::Create() callers

- Convert most callers to WebUIDataSource::CreateAndAdd().
- Construct WebUIDataSourceImpl directly in URLDataManagerBackend.
- Leave WebUIDataSource::Create() to be deleted separately.

Bug: 1206140
Change-Id: Id0d39c22f2beddd9c2eeae5fb17088d4055393fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4347827


Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118930}