Deployer: open pr on launch

[lubien]

Change Summary

What and Why: If our deployer image sets DEPLOY_CREATE_AND_PUSH_BRANCH we will create and push a branch with modified files

How: new env DEPLOY_CREATE_AND_PUSH_BRANCH

Related to: PaaS work

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Documentation

• [ ] Fresh Produce
• [ ] In superfly/docs, or asked for help from docs team
• [ ] n/a