PowerManagerServiceTest: Set dreams as supported & enabled by default

Some tests depend on dreams being supported & enabled.
This change sets the corresponding config values in the test setup.

Bug: 293660604
Test: atest PowerManagerServiceTest
Merged-In: I022f69f49ef0a7380a7d772b43db4ed7e3fb28b9
Change-Id: Ib3a7356ac29383a0452c78239f3a79cc08b21c59