feat: use docker caching during build

[laurentsenta]

• Add LABELS to our Docker images, which we use to list & cache relevant images,
• Pass the current master SHA when building (go|rust)-libp2p to prevent caching outdated master references,
• Add "simple" caching
• Add a cache_key option which you can use to mark special branches or skip caching in some cases (large test cases will fail with "no space left" errors)

TODOs

• Clarify notes from Use CI Caching during Interop Tests #31
• Merge related PRs
  • cmd: replace write-artifacts with output-composition option testground/testground#1440
  • .github/actions/setup-testground: shortcircuit testground setup #34
• drop DEBUG commit
• measure performances & stability