Bulk move annotations

## Feature Request Form
### As a user I'd like to bulk move annotations from public to private to group

Especially in classrooms, students often annotate the public layer before realizing they're not in the group. These annotations cannot be moved. They have to be copied, deleted and recreated in the group layer.

I also may have made private annotations that I want to make public. While this is possible on an individual level, it would be nice to do so in bulk.

### Allow selection and moving of groups of annotations presented in activity pages

### From a user:

>After a bit of embarrassment when I realized that no one in our group could see any of the highlights I thought were shared, I attempted to go through and update the privacy settings for each one. Sadly there's no way to bulk edit them, and editing each one takes at least 5 clicks and requires changing something other than the privacy setting as well (such as adding a comment or tag). It's just not worth the trouble to do this for hundreds of highlights.

The issue names activity pages as the entry point but provides no repository files or tests. Start by tracing how annotation selection and privacy changes are handled there; done means selected annotations can be moved between public, private, and group layers in bulk without editing each item individually.

Written by the indexing model from the issue text.