Allow editors and assistants to be assigned from the submissions summary panel

[NateWr]

Describe the problem you would like to solve
Managing editors want to be able to assign section editors to oversee submissions without leaving the submissions list, so that they can more quickly manage lots of submissions.

Section editors want to be able to assign copyeditors and production assistants without leaving the submissions list for the same reason.

Describe the solution you'd like
Allow participants to be assigned to a submission directly from the submission's summary panel in the submissions list page.

Who is asking for this feature?
This was a recommendation after user tests for #7495.

Additional information
This issue depends on the summary panel in #8883.

Assign editors button:

Opens a new side panel: