Avoid diffs when the only change is buildvcs metadata

[imjasonh]

Should be opt in

In a monorepo with many images, deploying may only rebuild the image to include a new buildvcs commit, and otherwise have no code changes.

At the same time, including buildvcs info is useful, and disabling it would be a loss.

The ko build diff could build before/after and determine if the only change is the buildvcs, and suppress the diff (avoiding downstream redeploy) if the only change was buildvcs

As work toward this, the resource output could include the metadata in https://pkg.go.dev/debug/buildinfo#BuildInfo so ko build diffs are richer and show dep changes etc in TF diffs

[StevenACoffman]

It would be ideal if the resource output included a sha256 of everything excluding the Go executable binary's metadata in https://pkg.go.dev/debug/buildinfo#BuildInfo

Looking at how go version -m [executable] works here  it mostly just runs buildinfo.ReadFile which has this nifty x.DataStart() which gives the virtual address and size  of the segment or section that should contain build information.
https://github.com/golang/go/blob/master/src/debug/buildinfo/buildinfo.go#L170