Add RollbackManagerService

This change adds RollbackManagerService as a new system service for
managing apk level rollbacks.

To work properly this requires additional selinux policy changes. Fails
gracefully in case of selinux denials, until we have a chance to sort
out the proper selinux policy.

Bug: 112431924
Bug: 116512606
Test: atest RollbackTest, with selinux enforcement off.
Test: atest CtsPermission2TestCases:PermissionPolicyTest
Change-Id: Id72aae9c4d8da9aaab3922ec9233ba335bc0198f