Do not throttle EXEMPT apps on battery saver

- Also keep track of # of callback calls and their duration and print them in
dumpsys. Example:

  Stats:
    UID_STATE_CHANGED: count=141, total=31.9ms, avg=0.226ms
    RUN_ANY_CHANGED: count=0, total=0.0ms, avg=0.000ms
    ALL_UNWHITELISTED: count=0, total=0.0ms, avg=0.000ms
    ALL_WHITELIST_CHANGED: count=0, total=0.0ms, avg=0.000ms
    TEMP_WHITELIST_CHANGED: count=28, total=14.9ms, avg=0.532ms
    EXEMPT_CHANGED: count=2, total=4.7ms, avg=2.370ms
    FORCE_ALL_CHANGED: count=6, total=1.1ms, avg=0.178ms
    FORCE_APP_STANDBY_FEATURE_FLAG_CHANGED: count=0, total=0.0ms, avg=0.000ms

Bug: 70565111
Test: atest $ANDROID_BUILD_TOP/frameworks/base/services/tests/servicestests/src/com/android/server/ForceAppStandbyTrackerTest.java
Test: atest CtsBatterySavingTestCases
Test: atest CtsJobSchedulerTestCases
Test: atest CtsAlarmManagerTestCases

Change-Id: Ie4983456dd60f7115a15ee25a8d1bf5c078dac74