Add exemption check for OP_SYSTEM_EXEMPT_FROM_SUSPENSION

If an app has the OP_SYSTEM_EXEMPT_FROM_SUSPENSION appop,
it cannot be suspended. Add the exemption to SuspendPackageHelper.

Bug: 246330879
Test: atest SuspendPackageHelperTest
      Manual testing with adb and Settings
Change-Id: I72b73324f64f330a9d1ee925dee64d42e0455548
(cherry picked from commit 9a276332)
Merged-In: I72b73324f64f330a9d1ee925dee64d42e0455548