Draft: WIP: new try with configTolerations

Previous attempt tried to evaluate all configurations for all zones (which resulted in important perf regression (roughly ×2).

This attempt only evaluates configTolerations and keep configurations optional (configurations are constraints not evaluated until a concrete config is added to envs: <zone>: configurations:. The impact on perf is minimal (and doesn't require huge refacto of conf to have fields defined in all contexts)

note:

• configTolerations should not depends on configurations to prevent evaluation cycles.
• files with TMP_ prefix are temporary, they are used to bench the current implementation without big rewrite
• the current POC only works for infra-stg

Eval time:

• with tolerations:

  ❯ time cue eval -t staging -t targeted_zones=infra-stg -e 'envs."infra-stg".configurations' > /dev/null
  cue eval -t staging -t targeted_zones=infra-stg -e  > /dev/null  14,48s user 0,26s system 149% cpu 9,829 total

• without tolerations:

  ❯ time cue eval -t staging -t targeted_zones=infra-stg -e 'envs."infra-stg".configurations' > /dev/null
  cue eval -t staging -t targeted_zones=infra-stg -e  > /dev/null  13,13s user 0,33s system 146% cpu 9,169 total