Feature: add lagoon-env configmap to advanced task spec

[bomoko]

Checklist

• [ ] Affected Issues have been mentioned in the Closing issues section
• [ ] Documentation has been written/updated
• [ ] PR title is ready for changelog and subsystem label(s) applied

Currently, advanced tasks don't mount the "lagoon-env" configmap, and so some variables that should legitimately be available to the task aren't. This PR adds it.

[bomoko]

@shreddedbacon - I've just assumed that the configmap will be available. Do we want to do a conditional check before loading?

[shreddedbacon]

@shreddedbacon - I've just assumed that the configmap will be available. Do we want to do a conditional check before loading?

Hmm, good question. Tasks do assume that an environment has deployed successfully to the point where a lagoon-env configmap exists, but an advanced task could theoretically run in an environment that is in a poor state where the lagoon-env configmap doesn't exist yet.

Perhaps something we should do is actually create the lagoon-env configmap when the namespace is created here

We basically do a "create if not exist" operation on the lagoon-env configmap to ensure it always exists?