Keep features up-to-date in the Feature Detail page

[KyleJu]

Implement a UI to show outdated feature warnings in the feature detail page. #4370. It shows a warning banner below the title based on the audience, if outdated.

For a feature author:

For a feature reader:

Follow-up

Send a follow-up PR for the case where a feature has not been verified since it is shipped.

[KyleJu]

@jyasskin This is a draft PR. Any opinions on the UI above? I can change the background color of the overview section and further highlight the warning, e.g.

[KyleJu]

@jrobbins A quick question on the TODO - do I have to iterate through stage.extensions to find all STAGE_TYPES_SHIPPING milestones?

[jrobbins]

LGTM after considering some name changes.

Also, please update the screenshots in the PR description because it seems that the wording of the messages was changed.

[jrobbins]

@jyasskin This is a draft PR. Any opinions on the UI above? I can change the background color of the overview section and further highlight the warning, e.g.

I think the all-orange overview box is too dark. Let's stick to just the warning banner above the overview.

[jyasskin]

I haven't reviewed the test in detail, and I try to avoid having opinions on colors, but the design looks good. Thanks!

[KyleJu]

LGTM after considering some name changes.

Also, please update the screenshots in the PR description because it seems that the wording of the messages was changed.

The screenshots in the PR description were updated, but my all-orange overview box comment had an updated screenshot.