manifest_parser_test needs more dedicated tests for output parameters...

Suggest updating the following test files to include outputs
- tests/dat/manifest_validate_singleline_params.yaml
- add multiple single line parm (types) and add to corresponding unit test.
- tests/dat/manifest_validate_multiline_params.yaml
- add multiple multi line parm (types) and add to corresponding unit test.
- tests/dat/manifest_validate_json_params.yaml
- add multiple json line parm (types) and add to corresponding unit test.

* please note that (for now) JSON output tests are not that interesting/unique, but in the future when we add support for JSON schema they will become more unique (and deserve dedicated unit testing).