Optimize presigning for replay.json

[ikreymer]

Fixes #2515.

This PR introduces a significantly optimized logic for presigning URLs for crawls and collections.

• For collections, the files needed from all crawls are looked up, and then the 'presign_urls' table is merged in one pass, resulting in a unified iterator containing files and presign urls for those files.
• For crawls, the presign URLs are also looked up once, and the same iterator is used for a single crawl with passed in list of CrawlFiles
• URLs that are already signed are added to the return list.
• For any remaining URLs to be signed, a bulk presigning function is added, which shares an HTTP connection and signing 8 files in parallels (customizable via helm chart, though may not be needed). This function is used to call the presigning API in parallel.

Testing:

1. Call clear presigned API endpoint to clear presigned.
2. Test by loading crawl or collection with large number of files (eg. Vice crawl).
3. Repeat with this branch and current main
4. Collection and crawls should load an order of magnitude faster with this approach.