libgralloctypes: support encoding and decoding

This adds a standard library that can encode and decode gralloc4
metadata. It is strongly recommended that all gralloc4 implmentations
and gralloc4 clients use this library for standard metadata types.

Bug: 141632767
Test: libgralloctypes_fuzzer
Change-Id: I5945ff54892fd8b4953b3758934947c3d599befc