Add app exemptions APIs for managing platform restriction exemptions

Add DPM.setApplicationExemptions API along with exemption constants.
Add DPM.getApplicationExemptions API
Add corresponding methods in DPMS along with map of DPM exemptions
constants to app-ops.
Add permission to AndroidManifest to expose to CTS tests.

Bug: 246330879
Test: atest ApplicationExemptionsTest
Change-Id: I1271db694af4091ead951d0167edac55ace92f47