Allow java_system_modules_import to replace java_system_modules

Previously, there were some places where a java_system_module_import
could not be used in place of a java_system_module. That was because
the code assumed a *SystemModules type not a *systemModulesImport type.
This change introduces a SystemModulesProvider interface that is used
instead and is implemented on both types.

Bug: 142940300
Test: m nothing
      ran new tests before changes to make sure they detected the issue
	  and after to make sure the changes fixed the issue.
Change-Id: I7b16ac5708880bdf61e6f5b1e6616c986f0ed763