Make Context.PERSISTENT_DATA_BLOCK_SERVICE public

As a new public API is added in PersistentDataBlockManager, and the
app uses context.getSystemService(...) to access the manager, change the
constant from @SystemApi to public.

Bug: 315380237
Test: m
Change-Id: Ie4bfb85c96184dba108faea601192894bbf32bb6
3 files changed