Add option for JSON formatted output

[HCastano]

Adds a new --output-json flag which will output build results in JSON instead of the
normal human readable format. This is useful for using cargo-contract in part of data
pipelines.

[HCastano]

Tbh I couldn't come up with good tests to figure out whether or not this flag worked as expected. They basically ended up boiling down to whether or not BuildResult had the right fields.

Open to suggestions though.

[cmichi]

Nice 👍!

[cmichi]

Suggested change

	assert!(res.serialize_json().is_ok());
	// then
	assert!(res.serialize_json().is_ok());

[cmichi]

Please add a

let expected output = /* Insert a multi-line string of the whole fixture */;
assert_eq!(serialized_json, expected_output);

You will have to replace some part of the absolute artifact paths in the serialized json (or use a regex).

Having a fixture for this will enable us to notice if the output format changes and communicate it in the changelog.

[cmichi]

Could you add this test back in? It ran the whole execution pipeline with OutputType::Json, which is not tested otherwise.

[HCastano]

I've pulled the CI Docker image locally and all the tests pass. Could the issues be caching related? cc @TriplEight

[TriplEight]

@HCastano if you run everything with cargo test --verbose --workspace --all-features and there's no special logic that would avoid running

failures:
---- cmd::build::tests_ci_only::contract_lib_name_different_from_package_name_must_build stdout ----
--------------------^^^^^^^^^^^^

this, then it might be caching related. You can compare the executed tests by cargo test -- --list

[TriplEight]

Just in case I've purged the caches and relaunched, now it's green, weird.

[cmichi]

Please add the execute test from 730d14a#r687601916 back in, looks good otherwise!