Slice permissions++

New permissions system for slices. Its up a little disk space at the
optimization of CPU/Mem usage, and most importantly doesn't have a
limit on the number that can exist.

Test: runtest --path frameworks/base/services/tests/uiservicestests
Test: runtest --path cts/tests/tests/slices
Test: manual grant through SliceBrowser
Bug: 77323760
Change-Id: Ie601bca042a7b28113a511383ca7e3a35c7c8c71