Add a first version of the setPolicy

The implementation of setPolicy in DevicePolicyManager is just
temporary, this CL focuses on the API of setPolicy itself.

FCRS_CODE: mdmwdjabuee391

Bug: 433950213
Flag: android.app.admin.flags.policy_streamlining
Test: CTS
Change-Id: I57b5a0f4ce68b24deaf052c5e9c5955a400a8637