Overhauls URL presigning by:
- cache the presigned urls in a flat, separate mongodb collection which
has an expiring index
- update presigned urls if not found / expired automatically in index
- remove logic on storing presignedUrl in files
- support cacheing presigned URL for thumbnails.
- add endpoints to clear presigned urls for org or for all files in all
orgs (superadmin only)
- supersedes #2438, fix for #2437
- removes previous presignedUrl and expireAt data from crawls and QA
runs
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Co-authored-by: Tessa Walsh <tessa@bitarchivist.net>
