Test for parsing CLI arguments in lfc

[patilatharva]

This PR adds a test that tests if the CLI arguments passed into Lfc match the values in the target properties Properties object which is passed to the generator. The test only checks that the desired values are passed to the generator and doesn't test the functionality of those values, because I believe that would belong in the LF unit tests and be out of scope for the CLI tests.

Rationale: #1641 - The bug fixed in #1631 showed that our current CLI tests are merely smoke tests and not sufficient to detect if arguments are passed properly.

Implementation notes: I preserved the structure of the existing CliToolTestFixture.java as much as possible, but chose to test by creating an Lfc object rather than using static methods. It seemed like the simplest way to gain visibility into the instance methods (which are necessary for Picocli), but let me know if there's a better way around this in Java.

[oowekyala]

Thanks for taking this on! I will push a couple of changes in the direction of my comments

[patilatharva]

@oowekyala thanks for the changes, it looks much better now!

[patilatharva]

@oowekyala just added a small fix to make the test ./gradlew test --tests org.lflang.tests.cli.LfcCliTest.testBuildParams pass - I instantiated lfc with injector.getInstance so the correct io would be passed in.

[lhstrh]

This looks pretty good! I left some minor requests for changes. Perhaps beyond the scope of this PR but good to do in the future would be to extend the tests to check the resulting TargetConfig as well.

[lhstrh]

This looks great! Thanks, @patilatharva!