[Ingest Manager] Integration Configurations should be constrained to be unique names

[EricDavisX]

Kibana version:
Testing with 7.8 BC 5 on June 4 2020 and it is confusing if there are configs of the same name. Ruflin may know more and have feelings on how we fix it, but thats the quick bug. I didn't see it logged, but I saw this for Data Sources and we decided to keep them separate since its a separate API call that needs to do the checking.

Describe the bug:
you can create config 'foo' and then create another config 'foo' and this can lead to problems, better to avoid it, even if it works and is not an architecture requirement currently.

Expected behavior:
a pleasant error message saying perhaps, "The name you entered is in use, please enter a unique name."

Screenshots (if relevant):

[elasticmachine]

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

[ruflin]

++ on making the config name unique.

[mostlyjason]

@ph We are finding ourselves needing to add extra columns to tables because we can't rely on the integration name being unique. Would be nicer to offer a simpler UX.

[jen-huang]

@jfsiii I think we completed this with recent work? Can you reference the PRs?

[jfsiii]

@jen-huang yes, the PRs are #79201 & #80506

[jen-huang]

@mostlyjason Closing as we completed this for 7.10 :)