Create testground end-to-end deals test that runs different versions against each other

[dirkmc]

Recently we had a bug where there was an incompatibility between the current and previous version of lotus, that prevented clients running the new version from making deals with miners running the previous version: #5608

As part of CI we should have a testground end-to-end deals test that runs the current master version of lotus against the version in the PR that triggered CI:

• master version of client <-> PR version of miner
• PR version of client <-> master version of miner

Tasks:

• Update testground to allow environment variables in testground composition files feat: support env vars in composition files testground/testground#1200
• Add composition files for the end-to-end testground deals test with differing client & miner version
  See lotus-soup compositions to test deals with different versions #5655 for a simplified version of what this would look like
• Update CI to pass the environment variables when running the compositions

Draft PR: #5707