Accompany HardwareBuffer with generation number

attachBuffer() should take a generation number and requestBuffer()
should return a generation number because AHardwareBuffer does not carry
the generation number.

Test: make cts -j123 && cts-tradefed run cts-dev -m \
CtsMediaTestCases --compatibility:module-arg \
CtsMediaTestCases:include-annotation:\
android.platform.test.annotations.RequiresDevice

Bug: 127778192
Change-Id: I201f84cf66f0e19b794a05c5ba88066360a37d96