[zircon][dev][goldfish] Add goldfish address space driver

Goldfish address space is a virtual device that is used
by AEMU to provide host visible memory when forwarding
Vulkan API from guest to host.

Goldfish address space is a PCI device that provides
a region of memory that can be used for mapping host side
memory into guest. Guest side Vulkan driver can reserve a
block of memory and use AEMU specific Vulkan API to map
host side memory into the block.

DX-939 #comment

Test: /boot/test/sys/goldfish-test
Change-Id: Ic6906c6f8d618bd8f31d49ad8838eb05a34b1ba9