Add ARM64 Github Actions test

[aaron-prindle]

Currently our Travis & Gihub Actions test only test AMD64. We should add specific testing around ARM64 in our Github Actions.

@briandealwis to add any additional information/requirements here.

[briandealwis]

I have been enabling buildkit to do multiple platform builds. That won't be necessary and should greatly simplify the tests setup (no hoops necessary to enable Buildkit).

The .travis.yml basically:

• installs Skaffold, container-structure-test, kind, and kubectl
• specifically runs some go tests (may no longer be necessary Custom test fails in multi-config as working directory is top-level directory #5666)
• runs a local build (skaffold build -p local) to verify the image builds fine
• starts a cluster
• launches ./run-its.sh to build test containers and run test jobs