Changes for RHEL9

[kberzinch]

This pull request is for #3580 and will not be merged until we have a RHEL9 box to put it on.

• Remove /storage/ directory from Docker build as most contents are not needed - an empty directory structure will be created as part of the build process
• App storage is always persisted within a Docker volume instead of either using a host volume or not at all
• Static assets are stored within a Docker volume instead of a host volume
• Worker and scheduler containers moved to poststart tasks to prioritize web container startup
• Nomad will attempt to reschedule the service indefinitely if it fails
• New Meilisearch key location
• PHP-FPM access and error logs are written to stderr instead of a file on disk
• Web container will attempt to remove an existing socket file if present
  • Pre-existing socket appears to cause an issue in at least some cases if the container restarts in-place
  • Removing it sometimes does not work because the socket is owned by a different user - not sure why
• Clean up some unused config options
• Add documentation on deploying Apiary from scratch as well as general backup and restore instructions (progress towards #3577)