Add batching for ReadGroups API invocation from DataSharingService

The ReadGroups API has a limit of 50 groups that can be fetched
in a single request beyond which it sends an error. Hence in chrome,
we need to break the list of groups into batches of 50 groups and
send them as parallel requests to server. This CL does that.

Bug: 401284543
Change-Id: Ibc73ba725eea2a55a97bf46ab5627ec1733e0e0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6335968
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1429720}