API clean-up around PacketSocketAddress

API clean-up around PacketSocketAddress:

1) Use of short / byte for enum ints in Java is awkward because
literals are "int", requiring casts. All constants in OsConstants
are defined as ints which also require casts. This commit moves to
int for PacketSocketAddress fields.

2) The constants to make sense of some PacketSocketAddress values
were missing and have been added to the Core Platform API.

Note that sll_pkttype is only set when receiving a packet, and there's
no function on Os that supports data and address to be returned (i.e.
there's no recvfrom() variant that allows for PacketSocketAddress) so
it's mostly useless and the associated constants have not been added to
@CorePlatformApi. If Android wanted to support PacketSocketAddress
fully then it's likely that the PacketSocketAddress will need to be
revisited (i.e. some or all fields made non-final) and the constants
can be exposed at that time.

Test: build / boot
Test: Removed the test from knownfailures.txt / ran OsTest on -eng build
with vogar
Bug: 135660232
Change-Id: I2ef79a3e18f6ffa890d897ac2db54f6fa8c0357a
5 files changed