Delete TurnOffWork 2.0 code

Most of the change just deleted dead code - the flag for the feature has
been hard coded as false and could only be manipulated via TestAPI that
was only used in already disabled tests.

To support upgrades from builds that had the feature turned on, this CL
preserves the functionality of unsuspending work apps during boot if
necessary. For that the now removed SPH.setPackagesSuspendedForQuietMode
is functionally inlined into DPMS code.

Bug: 306606563
Test: btest a.d.c.QuietModeTest
Test: atest com.android.server.devicepolicy.DevicePolicyManagerTest
Test: atest SuspendPackageHelperTest
Test: atest CtsSuspendAppsTestCases
Test: atest WmTests:ActivityStartInterceptorTest
Test: manual, OTA from early U build with the feature enabled
Change-Id: Ib9d749348f9b75b472aad479ad5eb9fff608f71b