i18n: externalize strings from 'app/views/layouts'

What does this MR do?

Re-opening of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6545/diffs.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
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• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
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