feat: migrate to rapidfort container

[RobHooper]

Closes #586

[jpmckinney]

Redis 6.2 is EOL since Feb 2025.

When operating a cluster, we can upgrade to at most 7.8 (though only 7.4 is at https://hub.docker.com/_/redis/): https://redis.io/docs/latest/operate/rs/installing-upgrading/upgrading/upgrade-cluster/#supported-upgrade-paths

However, the Docker images are not a cluster, so I think we can upgrade directly to 8.4. For example, 8.0x can read 6.2 databases: https://redis.io/docs/latest/operate/rs/installing-upgrading/upgrading/upgrade-database/

That said, we can still take the precautions here: https://redis.io/docs/latest/operate/oss_and_stack/install/upgrade/standalone/

I've read these breaking changes and found no issues:

• 6.4 https://redis.io/docs/latest/operate/rs/release-notes/rs-6-4-2-releases/
• 7.0 https://redis.io/docs/latest/embeds/r7-breaking-changes/
• 7.2
  • https://redis.io/docs/latest/develop/whats-new/7-2/#breaking-changes
  • https://redis.io/docs/latest/embeds/r7.2-breaking-changes/
  • https://redis.io/docs/latest/operate/rs/release-notes/rs-7-2-4-releases/rs-7-2-4-52/#breaking-changes
• 7.4 no breaking changes
  • https://redis.io/docs/latest/develop/whats-new/7-4/
  • https://redis.io/docs/latest/operate/rs/release-notes/rs-7-4-2-releases/
• 7.8 https://redis.io/docs/latest/operate/rs/release-notes/rs-7-8-releases/#breaking-changes
• 7.22 no breaking changes: https://redis.io/docs/latest/operate/rs/release-notes/rs-7-22-releases/
• 8.0
  • https://redis.io/docs/latest/develop/whats-new/8-0/#breaking-changes
  • https://redis.io/docs/latest/operate/rs/release-notes/rs-8-0-releases/#breaking-changes
• 8.2 no breaking changes: https://redis.io/docs/latest/develop/whats-new/8-2/
• 8.4 no breaking changes: https://redis.io/docs/latest/develop/whats-new/8-4/