[ML] File upload card sometimes missing on Kibana home page

[pheyos]

Sometimes, the Kibana home page doesn't display the Upload a file button even though the user has the needed permissions.

Can e.g. be seen a couple times in this flaky test runner job.

Might be related to the changes made in #77745

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[pheyos]

This issue makes the functional permission tests fail, so I've disabled them until this issue is solved:

master: 1b26c90
7.x/7.10: a9c0969

[walterra]

Some investigation:

• registerFeature() adds the file import panel on Kibana's home page.
• In ml/plugin.ts this has always been called in the callback for the license subscription (an async callback).
• With the changes in [ML] Limit exposing shared static code through ml/public/index.ts. #77745 we added remote data fetching to reduce the bundle size of the page load bundle. This increases the time it might take to get to the code that does the registers. This results in a race condition which triggers the failing test.
• It is worth noting that the overall structure of the code (registering in an async function after the license check triggers). It seems to me until now we've just been lucky enough that this wasn't triggered.

This investigation is still work in progress, will further dig down.