Add ExtendableType to allocate

Allows for passing arbitrary additional options to IAllocator
Can be used to control things such as compression level without
exhausting usage bits

Currently there are no standard options defined so this only allows
for vendor-internal extensions currently.

Fixes: 257075040
Test: VtsHalGraphicsAllocatorAidl_TargetTest
Change-Id: I37b730f5ba141b08d458866c6d03a39b27124e02