Use GetInstance to load feature flags instead of rill.yaml

[AdityaHegde]

closes #4763

We cannot use repo APIs in cloud to get rill.yaml. Feature flags was moved to GetInstance. This PR updates to make use of GetInstance.

[briangregoryholmes]

If this PR is not a release blocker, I think it would be a good time to solidify our precedence for different feature flag methods going forward.

I'm of the opinion that we should remove setting feature flags via localStorage or the URL. If others say we need to maintain that, then we'll need to change the feature flag implementation so that certain flags cannot be "overridden". For instance, you might set exports to false in a rill.yaml and a user should not be able to force this to true by appending something to the URL. But that may not be true of every feature flag. Currently, there's this idea of system vs user, but I think we should change this scope idea to rill vs user and then add an additional method/property to determine whether something can be set via the URL or localStorage.

@ericpgreen2

[AdityaHegde]

Good point. Ideally we should have a check in the backend as well. Because it is trivial to force change it on client side and still enable export.

[AdityaHegde]

@begelundmuller Since the issue was with an incomplete release, do you think this is a blocker still?

[begelundmuller]

@begelundmuller Since the issue was with an incomplete release, do you think this is a blocker still?

I don't think it should be a release blocker

[ericpgreen2]

If this PR is not a release blocker, I think it would be a good time to solidify our precedence for different feature flag methods going forward.

I'm of the opinion that we should remove setting feature flags via localStorage or the URL.

@ericpgreen2

I'm game for this. Both setting flags via local storage and via URL preceded our ability to set flags in rill.yaml. It'll be simpler to have just one way of operating. Both ourselves and customers can handle rill.yaml.

[ericpgreen2]

Approving, since removing URL & local storage feature flag support can always be done in a separate PR.