Use the new file icons from gitlab-svgs in the Repository Browser
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### Proposal
> Add a feature flag which if enabled serves the resulting `dist/file_icons.svg` rather than `app/assets/images/file_icons.svg` *and* uses the new `getIconForFile` from this package rather than `file_icon_map.js`. (The code should be the same as of now, as I just rebased.)
in https://gitlab.com/gitlab-org/gitlab-svgs/-/merge_requests/709#note_997861560
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issue