Add check that `go generate` do not produce changes for the branch

[denis-tingaikin]

Motivation

When we add a patch for the govpp we should make sure that we don't have a diff when run go generate.

TODO

• Add a ci job for checking that go generate doesn't produce any diff

References

Incident #29
Similar job https://github.com/networkservicemesh/.github/blob/main/.github/workflows/cmd-gogenerate.yaml

[VitalyGushin]

@denis-tingaikin Seems like the desired behaviour is already implemented here:

govpp/.github/workflows/ci.yaml

Lines 107 to 111 in 3c0a753

	- name: Generate files
	run: go generate ./...
	- name: Check for changes in generated code
	run: |
	git diff -- binapi || (echo "Rerun go generate ./... locally and resubmit" && exit -1)

[denis-tingaikin]

It seems like it doesn't work; see #27. There is green CI, but actually go generate was required. That is what we did after #29