scanner: file browser in the sunburst/dashboard output

It would be useful to be able to drill down into directories reported as known/unknown in the sunburnt dashboard/output. For instance, if a dir is 99% known with a single unknown file, one would really want to known which one that is, with it's path and a link to it to open it (via the native browser way of displaying it, no need to create an ad-hoc renderer).

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Migrated from T2364 (view on Phabricator)