Change the way modules are configured:
Add dependencies on other modules instead of adding additional package fragment providers
Refactor related code
Drop DependencyKind
Hide common new module creation in CliLightClassGenerationSupport
Specify visibilities and reformat surrounding code
Add test checking that there is no internal visibility specified in stdlib sources
Internal visibility does not make sense in stdlib
because it is either missed public or private would be more appropriate
Ilya Ryzhenkov