Is your feature request related to a problem? Please describe.
In Storage, a list objects operation returns a response body with both a list ofitems andprefixes. The list of items are objects ordered lexicographically by name, whereas the prefixes operate like a directory listing.

Thestorage objects.list API allows a query paramaetermaxResults that represents the maximum combined number of entries initems[] andprefixes[] to return in a single page of responses.

While theIterator class supportsmaxResults, it only accounts for the maximum number of items.

Describe the solution you'd like
Is there a way to haveHTTPIterator.max_results andHTTPIterator.num_results account for results other than items from the response body? Currently, only items are kept count fornum_results and consequently_has_next_page()

    def _items_iter(self):        """Iterator for each item returned."""        for page in self._page_iter(increment=False):            for item in page:                self.num_results += 1                yield item

GCS objects.list API call returns a response body with the following structure:

{  "kind": "storage#objects",  "nextPageToken": string,  "prefixes": [    string  ],  "items": [    objects Resource  ]}

Additional context
Customers are concerned running into memory issue when all prefixes are returned and max_results doesn't take any effect. Internal b/401531977

it = client.list_blobs(    bucket_name,    delimiter='/',    prefix="some_prefix_pattern",    max_results=100,)list(it)print(len(it.prefixes)) # All 755 prefixes are returned regardless setting max_results=100