Move add-to-whitelist APIs.

Move addToPowerSaveWhitelist to PowerWhitelistManager and rename the
method.

Bug: 138239060
Bug: 140141678
Bug: 144864180
Test: atest PowerWhitelistTest
Change-Id: I7ae16c48e2eb3a5aa66e7e44dfca05b942e65741
4 files changed