toolchain: Remove legacy proto interfaces

BUG=b:187794927
TEST=./generate.sh

Change-Id: I537e712327b5db4b64cb2827d6b38659b2409c18
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/3344436
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Denis Nikitin <denik@chromium.org>
9 files changed