Run the given callback only inside `runOnPageScrollsInitialized`

Let `PagedView.runOnPageScrollsInitialized` run the given callback only
instead of running all the current existing callbacks inside
`mOnPageScrollsInitializedCallbacks` once `mPageScrolls` has been
initialized.
All the existing callbacks will be run by
`PagedView.onPageScrollsInitialized` instead.
By doing this, we can avoid some unexpected crash while running
the pending callbacks in some scenarios. E.g., removeAllViews.

Flag: EXEMPT fix a regression
Bug: 385612978
Test: Manual
Change-Id: I0877cff752aabd1569dd54a9d04001687f90a5f6