sdk_version: "module_current" is supported

module_* is a new API surface for OS modules (e.g. APEXes). It has
slightly bigger API surface than the system_* SDK. Specifically, APIs
with @SystemApi(client=MODULE_LIBRARIES) are added there.

Bug: 146757305
Test: m

Change-Id: I8980e50c0e3a4cd843048e0de1f638e854384f46