Improve stress-test container start order and make default compose allow multiple buildgrid instances with nginx-load-balancer

Description

WIP

• Improve stress test start order by using a script to wait until the expected services are up (bots and clients wait for buildgrid to be up now)
• Improve database initialization by having a separate buildgrid instance with "automigrate: true" when a database is needed, and make other buildgrid instances wait on that one to perform the migration/database creation
• Extend the compose file to allow for a load balanced buildgrid (which will help with testing permissive bot session etc) (clients/bots should just connect to buildgrid-lb host and nginx should perform the "load balancing")
• Fix worker start script by specifically disabling the localcas protocol (new breaking default for the worker)