Replacing the direction page with better issues views

I'm concerned with having duplicated functionality between issues index and this page, so I propose that we make it the same page.

This can be achieved by adding the following functionality to https://gitlab.com/groups/gitlab-org/issues, which will be interesting for everyone using the issues index page:

• Group by milestone
• Minimal view (only show the issue title and project and don't use pagination)

We can already sort by label, and this wouldn't duplicate functionality and retain the existing functionality like search and more filtering options.

We shouldn't sort by label popularity, but rather wait for label priority (8.8) and introduce further specification by then.

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