I'm not sure why cargo_embargo.json wasn't ever checked in, but I
reconstructed it as best I could.

Also replace LICENSE file with a symlink to LICENSE-APACHE to match the
crate archive contents.

Bug: http://b/339424309
Test: treehugger
Change-Id: I9a79e8c01c69fb0089d0574faa5172d1db8377b5