Add feature flags for new Lagoon features

[smlx]

These feature flags integrate with these Lagoon PRs:

• https://github.com/amazeeio/lagoon/pull/2523
• https://github.com/amazeeio/lagoon/pull/2536

They are tested in those PRs too.

The feature flags are documented here:

• https://github.com/amazeeio/lagoon/pull/2541

And chart support was added here:

• https://github.com/uselagoon/lagoon-charts/pull/234