Port extended-availability-zone API into v3 part1

This changeset only copies the v2 files into the appropriate v3
directories unchanged. The copy as-is will not be loaded by either
the v2 or v3 extension loaders. The second changeset will then
make the changes required for it to work as a v3 extension.

This is being tried in order to make reviewing of extension
porting easier as gerrit will display only what is actually
changed for v3 rather than entirely new files.

Partially implements: bp v3-api-extension-versioning

Change-Id: I531a2d2f68a268d44eaef3a5af0a9c799787b188
Merge "Port extended-availability-zone API into v3 part1"