Issue #3626897: Uploads fail on multi-server hosting because files are staged in temporary:// and saved in a separate request

Scot Selfrequested to merge
issue/filebrowser-3626897:3626897-upload-staging-shared into 3.1.x

Issue #3626897 by scotwith1t: Uploads fail on multi-server hosting because files are staged in temporary:// and saved in a separate request

Closes #3626897

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