implement new upload styles in new files

closes CNVS-15365

until OPS-442 goes through this will need to be tested locally using local
uploads, or on an S3 instance that accepts 'content-type' headers

also makes naming conflict dialog focus the primary button, and if not
there, falls back to the close button

test plan:
  - enable new files
  - navigate to the course files
  - select the 'Upload' button on the toolbar
  - select one or more files to upload
    - files should upload successfully
    - naming conflict window (if needed) should continue to work
    - upload progress should be displayed

Change-Id: I997a7619190efa8f5601475cdacd3f5fd849bb71
Reviewed-on: https://gerrit.instructure.com/40809
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Clay Diffrient <cdiffrient@instructure.com>
Product-Review: Jason Madsen <jmadsen@instructure.com>
QA-Review: Jason Madsen <jmadsen@instructure.com>