Update CPU GPU headroom HAL API

* change pid to tids list
* add configurable interval value
* change float (array) return type to union type
* add default values for the params

Bug: 346604998
Flag: EXEMPT HAL changes
Test: atest VtsHalPowerTargetTest
Change-Id: I4422b8489da5bf072ad821d04f91fcfabccf9d98