Fixed summary data for closed iterations

What does this MR do?

FE for #233707 (closed)

Change iterations summary query to use report.stats, which means the values are fixed once the iteration is closed.

1. Move iteration_report_summary.vue => iteration_report_summary_open.vue, still uses the old query
2. Create iteration_report_summary_closed.vue for closed iterations, uses the new report.stats query
3. Add shared iteration_report_summary_cards template to render cards for each of the above 2 items
4. Conditionally render open/closed component based on iteration.state

Doesn't do the following:

• Show Assigned (in progress) count, see #233707 (comment 429843086)
• Toggle weight in summary when toggling in burndown charts (adding in !48659 (merged))
• Move summary below the total/weight toggle button (adding in !48659 (merged))

Leaving those two tasks for followup issue as I need resolve some iteration/burnup dependencies

Screenshots (strongly suggested)

before	after

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content