test_vendor: Add PacketView for copyless parsing

A View is holds bounds and a shared pointer.
A PacketView is a forward list of View, templated for endianness.
A BaseIterator iterates over PacketViews.
An Iterator is a BaseIterator with extract, which is templated for endianness.

Test: rootcanal-packets_test_host
Change-Id: I68d6502861be61f411c0f5f2da33ead3d2392694