Update workshop automation for Sensu Go 6.5.0

[calebhailey]

Changes:

• [x] Use the new sensu-backend init --cluster-admin-apikey automation
• [ ] ~Rename the configurator service to workshop (which can also now be used as a sandboxed workstation environment)~
• [x] Remove the sensuctl container (no need for sensuctl configure thanks to automated API Key initialization)
• [x] Remove the wait-for-sensuctl script and .config/ volume mount
• [x] Refactor the seed-workshop-resources script (use a simpler sensuctl retry loop mechanism)