Update engine to pass error details (for both terminal and non-terminal errors) via stdout

[Gordon]

Return codes:
0: success => resources.yaml is updated based on input constraints
1: failure => resources.yaml is NOT updated, this was a permanent failure that prevented solving

• These occur when the engine returns an error (ie, execution halted)

2: invalid => resources.yaml is updated based on the input constraints, but one or more properties fail validation

• These are pulled from Decisions (ie, do not halt execution)