DO NOT MERGE Extreme battery saver experiment

PS1 is just a squashed cherry-picks of:
- https://googleplex-android-review.git.corp.google.com/#/c/platform/frameworks/base/+/2808591/
- https://googleplex-android-review.git.corp.google.com/#/c/platform/frameworks/base/+/2542212/

Test: Tested manually
Bug: 64976537
Change-Id: I99f93471e348bdd31ac08fbd91b27bab8c8e498b
(cherry picked from commit d8a9b29e12b4ef45e6d66fcc54038adfc6c8fdbf)