Extract sidebar markup into helper

[Benabik]

Description

The markup for the sidebar was copy/pasted many many times. This PR adds the following helpers:

• sidebar - simply adds the appropriate ul wrapper for the sidebar to its block, which should have the other two helpers.
• sidebar_item - Ensures that whenever the current page is the linked path, the item is active. Has an optional argument to be active for any path on the controller.
• sidebar_group - Takes a list of items and ensures the group is open whenever any item under it is active. Can also take a controller similar to the item, useful if the sub-items are only some actions on a controller.

Notably, this fixes:

• Several instances where the path checked was not the path linked
• Several places where an item would be active in a group that wasn't
• The active checks in the admin sidebar all missing the admin/ prefix

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Manually clicking on all the sidebar links and verifying they go to the correct place and highlight afterwards

[awwaiid]

I'd like to hold off on this refactor until after / separate from the dashboard update.

[dorner]

This has been sitting for a long time. Dashboard has been merged now. I'm going to close this for now - I'm fine with reopening if there's desire to.