Filter Group by shard

Context

As part of migration to new Gitaly servers we need to drain 3 types of repositories off a Gitaly storage:

1. Project Repositories: https://docs.gitlab.com/ee/api/project_repository_storage_moves.html#schedule-repository-storage-moves-for-all-projects-on-a-storage-shard
2. Snippet Repositories: https://docs.gitlab.com/ee/api/snippet_repository_storage_moves.html#schedule-a-repository-storage-move-for-a-snippet
3. Group Repositories: https://docs.gitlab.com/ee/api/group_repository_storage_moves.html#schedule-a-repository-storage-move-for-a-group

Problem

We want to start migrating the group wikis off 1 specific storage onto the new Gitaly servers that we are going to create in https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/935. For GET /projects admins can filter by repository_sotrage.

For GET /groups we don't have a way to filter for the storage, so there is no way for us to control which wikis we migrate.