Add status checks report to the merge request reports tab

What does this MR do and why?

Adds StatusChecksProvider, StatusChecksNavItem, StatusChecksPage, and StatusChecksContent, following the code quality report pattern, plus a View report button on the status checks widget. The summary logic moves into a shared utils.js used by both the widget and the report.

report_section.vue is a shared component that every report on the Reports tab uses. It used to render each row's supportingText as plain text, so the style markers (%{small_start} and %{small_end}) that the status checks rows put in that field showed on screen. It now passes supportingText through generateText, the same helper the component already used for the row's text field. generateText escapes HTML before it converts the markers, so this does not create live markup.

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