Enhance admin BetaTestApplication and OpenEdXInstance admin pages
Created by: xitij2000
This PR makes some basic improvements to the admin pages for Ocim.
It adds the instance name, email, status and days since activation for beta registrations to make it easy to get all that information in one place. It also adds support for filtering by beta registrations by status and searching registrations by name, email and domain
The admin page for OpenEdxAdmin now also displays whether the instance is successfully provisioned, and allows searching by internal_lms_domain.
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