[Ingest Manager] Remove epm feature flag

[mostlyjason]

Currently, we have a feature flag in kibana to enable EPM. However, we don't tell customers what EPM is and it's not shown in the UI anywhere. Its a little confusing what that is referring to. We should remove the flag or make it more clear what it's referring to.

#66736

[elasticmachine]

Pinging @elastic/ingest-management (Team:Ingest Management)

[ruflin]

++ on removing the flag altogether.

[jen-huang]

@ph @mostlyjason Hi, in addition to xpack.ingestManager.epm.enabled, we also have xpack.ingestManager.epm.registryUrl setting which has the same confusing usage of "epm". I suggest to:

1. Remove EPM enabled flag
2. Flatten the registry url flag to xpack.ingestManager.registryUrl

What do you think?

[ph]

+1 for the proposal. We might to update the docs with that new flag.

[mostlyjason]

+1

[jen-huang]

Thanks everyone for the quick consensus. This wasn't a high priority in our backlog, but if a user has invalid/unknown settings in their config, Kibana will fail to start. I opened a PR for this change to avoid this kind of breaking change after beta release.