Umami views should use responsive grid

Problem/Motivation

Umami uses themed unformatted lists to get a 'responsive grid layout', but since 10.0.0, we've had an actual responsive grid in core, so we should use that instead.

If we're lucky, this might just be reconfiguring the views, then locating and deleting any unnecessary CSS.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet