Use iteration dates as primary display attribute

What does this MR do and why?

We are going to use iterations dates as the primary display attributes over title as users often think of iterations in terms of their dates. Title is also going to be an optional attribute and we will gray out the title attribute to give it less prominence. #349612 (closed)

How to validate and screenshots

Check out the following places with and without the FF :iteration_cadences.

- The iteration cadence list page
- The iteration show page

Before vs After for iterations lists/show

With :iteration_cadences FF enabled:

Location	Before	After
Iteration cadences		(note the absence of titles)
Iteration (show)

with :iteration_cadences FF disabled:

Location	Before	After
Iteration cadences
Iteration (show)

Before vs After for board and issues list filtered search

Visit any board or issues list and use the filtered search for iterations AFTER enabling the below FFs:

Feature.enable(:issue_boards_filtered_search)
Feature.enable(:vue_issues_list)

:iteration_cadences FF do not affect the next changes:

Location	Before	After
Board Filtered Search (requires FF :issue_boards_filtered_search)
Issues List Filtered Search (requires FF :vue_issues_list)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.