Engine: break out Env utilities into their own type - Env
Engine: Output.AddEnv decodes structured data from the standard output of a job
Merge pull request #3117 from shykes/engine-refactor-env

Engine: break out Env utilities into their own type - Env
Merge pull request #3118 from shykes/engine-structured-output

Engine: jobs can send structured output as json on stdout