Verbose mode for echo to expand templates used.

Right now echo is treating used templates as first-class components.

This means that the output of:

benthos -t "./templates/*.yaml" -c ./config.yaml echo

does not show the values that where used from the template. So when following the example on the templating page the output of:

benthos -t "./templates/*.yaml" -c ./config.yaml echo

is:

input:
  label: ""
  aws_sqs_list:
    urls:
      - https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue1
      - https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue2

It would help with writing complex templates to add echo_verbose or another method so that the output of the above command would be:

input:
  broker:
    inputs:
      - aws_sqs:
          url: https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue1
          region: us-east-1
      - aws_sqs:
          url: https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue2
          region: us-east-1

Currently the only way to see if your template is working is by running the config, that is not always desirable.

Start with the benthos ... echo command and the templating page linked in the issue. Determine how an expanded-template display mode should be exposed, then verify that running the command shows the resolved input structure without running the configuration. No source files or tests are named, so locating the CLI and its existing echo behavior is required.