Add java_system_modules to sdk/module_exports

Adds an SdkMemberType implementation for java_system_modules. It
specifies that java_system_modules can be used with sdk as well as
module_exports, and also that the libs property should be included
as transitive members in the sdk.

It also adds support for treating appropriate tagged properties in
the snapshot prebuilts module as references to sdk members so that
they are correctly transformed when creating the versioned modules.

Bug: 142940300
Test: m nothing
Change-Id: Ic10b5a6d5b92b6018334fe876f06feaf79cc55e9