Add plugin-level filtering to Updates page when viewing per tag

When managing updates across multiple sites using staged rollout rings (tags), I need to update specific plugins across all sites in a single update ring at once. Currently:

• The 'per item' view shows each plugin with all sites, but doesn't allow filtering by tag

• The 'per tag' view groups by tag first, then sites, then plugins—requiring me to expand each site individually to find and update a specific plugin

What I’d like: A way to view updates grouped as Tag → Plugin → Sites, so I can:

1. Select my update ring (tag)

2. See all plugins needing updates in that ring

3. Update a specific plugin across all sites in that ring with one action

4. Then move to the next update ring and repeat

This would enable efficient staged rollouts where I update one plugin across Ring 1, then Ring 2, rather than updating all plugins on one site at a time.