Turn On Flexibility Controller

Turning on the feature flag in Flexibility Controller by turning the
default value of Flexibility_Enabled to true.

Bug: 244626492
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/job
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/job
Test: atest CtsJobSchedulerTestCases
Change-Id: I757bbb3af7142006070b10610c9df9a959df997c