Latest links updates (#1976, #2000)

[daveoconnor]

This is related to tickets #1976, #2000, and boostorg/website-v2-docs#551.

This PR:

• Provides better handling of the latest links with a "chain of responsibility" of path matchers.
  1. Filters on regex and only after a match then looks up the db/s3 for matching destination paths providing, otherwise moves on to the next matcher.
  2. Allows easy additions of handlers and easy reordering of the handlers
  3. Adds tracking of handlers on a per request basis, so we can prioritize based on concrete metrics and add additional handlers if warranted.
• Adds a way for admins to start a rolling refresh of RenderedContent when it's not urgent, say a new matcher has been created. The previous task to delete all cached content quickly remains.
• Adds kubectl and a link to documentation on accessing the staging pods etc.
• Fixes an issue with user creation in load_production_data.sh that arose because there were additional DBs being downloaded.
• Fixes an issue with rendered content modified dates not getting updated on refresh.
• Updates pycharm debug libs

Design decisions: we use an int to store the latest match indicator and only store paths if not a direct match, as requested in #1976.