Remove Java runtime classes from kotlin release.

Because we build lite and core totally separately, they can't both be depended on without producing conflicts.  Our kotlin setup has been doing exactly this for a long time though, in order to share code between kotlin and kotlin-lite.  Even *with* this change, it's invalid to depend on both lite and core, because they contain different builds of our boostrapped protos.  However, they now share the internal `lite_runtime_only` target, which kotlin can reuse to share code.

This prevents `lite` from getting linked into kotlin, allowing kt_jvm_export to properly strip out all classes from the Java runtime.

Fixes #20566

PiperOrigin-RevId: 734387194