Remove EXIF data from existing uploads

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/55469

Except from removing EXIF from any new uploads we should also removing EXIF data from existing uploads.

Possible solution: create a background migration (or rake task) which will select all uploads which have path matching .(jpg|jpeg|tiff) suffix, fetch these uploads, remove EXIF data (mini_magick gem can do this) and write data back again to the original location

Note that issue should be release in the same release as https://gitlab.com/gitlab-org/gitlab-ce/issues/55469 because it's a security issue.

Downstream issue: https://dev.gitlab.org/gitlab/gitlabhq/issues/2810

/cc @dappelt @smcgivern