Aux Files: Add some checks to aux files on upload

[kcondon]

Add file validation: particularly duplicate names, which when occurring on the same tabular file results in a 404 on download. Name is comprised of format tag+format version.

Potentially add file size and file count limits.

[qqmyers]

Also have a fix for this. Awaiting the changes from #7729 to make a PR.

[djbrooke]

I'll close based on the third bullet in #8237 (comment) ("The API will block attempts to create a duplicate auxiliary file") - please reopen if this is not the case. We can revisit the count and size limits if this gets more widely adopted.