Add list mode to merge request file tree

Iterating on #14249 (closed)

There are benefits and disadvantages to file trees vs lists, but people have strong opinions one way or another. A particularly advantage of lists is that they are more compact for changes that span many levels of directories. We should allow users to choose.

Proposal

• Add a file list mode to the file tree.
• Remember the user preference so that all merge requests are shown the same way.

Designs

Inline diffs	Side-by-side diffs	Filter files

• The file list items show the full path and are truncated at the beginning so that the file names are intact.
• When the filter files text input receives focus, the list/tree toggle buttons are hidden and the text input is made full width of the file browser pane. This is to prevent the user from changing list/tree modes when viewing the filter results.

Links / references