Attempt to deprecate redundant usesPermission data structures.

Considering a map of permision name to the ParsedUsesPermission object
is already stored, we no longer need to keep track of a set of
permission names. This can just be derived from the keyset of the map.
The getRequestedPermissions() method is kept to avoid several changes
throughout the codebase; it also helps provide a nice abstraction to get
the permission names without accessing the map and calling for the
keyset explicitly.

Similarly, the list to store the ParsesUsesPermission objects can be
deprecated in favor of deriving the information through the map's
values. Some use cases had to be adjusted to not use the get() method
since the .values() of the map returns a Collection not a List.

Bug: 419394776
Test: presubmit; verified a few sys health tests via ABTD
Flag: EXEMPT refactor
Change-Id: Ic3abefb5f8c1b2b40620969d4038a4c555fe9cc0