Move the installed plugins list from the admin UI to the primary UI

[jeremystretch]

NetBox version

v3.7.0

Feature type

Change to existing functionality

Proposed functionality

NetBox currently lists all installed plugins under the admin UI (/admin/plugins/installed-plugins/). Replicate this view in the primary UI, under the "admin" menu section.

Use case

Users will be able to inspect plugins without leaving the primary UI, and unblocks #12325.

Database changes

None

External dependencies

None