Improve error list UI on mobile viewports

Problem

Error list page is difficult to use in mobile viewports. It currently looks like this:

Screen_Shot_2019-10-18_at_11.29.24_AM

Reproduction Steps

Go to https://gitlab.com/gitlab-org/release-tools/error_tracking using a mobile viewport.

Solution/Design

Errors_List_View_Mobile_Current

Designs on Sketch Cloud

Sketch Measure Specs

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