refactor: rewrite activestandby task to remove external dioscuri requirement

[shreddedbacon]

General Checklist

• Affected Issues have been mentioned in the Closing issues section
• Documentation has been written/updated
• PR title is ready for inclusion in changelog

Database Migrations

• If your PR contains a database migation, it MUST be the latest in date order alphabetically

The existing activestandby task has a heavy dependence on dioscuri which is becoming difficult to maintain.

The goal of this task is to incorporate the functionality of dioscuri into the activestandby task that Lagoon performs. Initial support was rolled into the remote-controller under uselagoon/remote-controller#148 which allows for this new task to do the functions it needs between the two namespaces.

What this task also does is replace the older labels on ingress from dioscuri.amazee.io to activestandby.lagoon.sh.

Also new, is when the migrations are being performed, it will add a new label activestandby.lagoon.sh/migrating=true to indicate that the migration is taking place. Once the migration has taken place, it sets it to false. This is so that other systems that may look at ingress and perform functions can potentially use this new label to take action on something, or prevent something from happening when the ingress are moved between namespaces.

Note: This has a dependency on remote-controller v0.15.4, which is contained in lagoon-remote 0.86.1 or greater.

Closing issues

closes #2607

[tobybellwood]

I'm happy with this from my side. It'll be good to get it into test infra against previously migrated routes to confirm.

This will need an entry in deprecations.md to signal the removal of disocuri as an external dependency.