Implement Pager resumption even through into_pages

By design, we didn't support resuming `Pager` (`ItemIterator`) but, upon further discussion, decided we can but will resume from the current page until all items on the current page are processed.

This also fixes a problem that, because of the design, we didn't pass through resumption to the `PageIterator` at all - it couldn't even resume as a `PageIterator` for subsequent pages.

Author: heaths

sdk/core/azure_core/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Features Added
 
+- Added `ItemIterator::continuation_token()` and `with_continuation_token()` to resume paging items. The current page is restarted until _after_ all items have been iterated.
 - Added `Response::to_raw_response()` function to create a `RawResponse` from cloned data.
 - Added `UrlExt::append_path()`.
 - Implemented `IntoFuture` for a `Poller`. Call `await` on a Poller to get the final model, or `into_stream()` to get a `futures::Stream` to poll the operation manually.
@@ -25,6 +26,8 @@
 
 ### Bugs Fixed
 
+- `ItemIterator::into_pages()` now properly supports resuming from the current page until _after_ all items have been iterated.
+
 ### Other Changes
 
 ## 0.29.1 (2025-10-06)