Stop doing shallow clones of protos

This cleans up all of the `go vet` issues that currently plague
infra/go. We're not supposed to be copying proto structs by value.

This is more fallout from me recently upgrading chromiumos/infra/proto
to use the modern protoc-gen-go plugin.

BUG=chromium:1165962
TEST=run_tests

Change-Id: If18940d5218fc960e8bf1a88b6c88010f5c5317e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/go/+/2685422
Commit-Queue: Jack Neus <jackneus@google.com>
Tested-by: Sean Abraham <seanabraham@chromium.org>
Auto-Submit: Sean Abraham <seanabraham@chromium.org>
Reviewed-by: Jack Neus <jackneus@google.com>
23 files changed