[ntp-composebox] Send error status updates for invalid files

There is already handling for server response errors, but this cl adds handling for client-side proprocessing failures for file uploads.

Bug: 430053361
Change-Id: Ib6323422185b3384ca01a1706587b4a1050605d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6757243
Commit-Queue: Jason Hu <hujasonx@google.com>
Reviewed-by: Roman Arora <romanarora@chromium.org>
Reviewed-by: Nihar Majmudar <niharm@google.com>
Cr-Commit-Position: refs/heads/main@{#1487752}