port Attach_interface 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.

Change-Id: I83803ed04f39cb7dda537d08d34e78a04cd64d4c
Merge "port Attach_interface API into v3 part1"