Test current PR build and add local registry in KinD

[matzhaugen]

Test current PR build and add local registry in KinD

Description

This PR does a few things:

1. Tests the current faas-netes image in the integration test with the KinD cluster in the CI job. I use a github action for setting up the kind cluster.
2. The kind cluster adds a local registry to which we push the fresh image from the current PR.
3. Separates the multiarch build with buildx and the integration test and thus reduces the PR build time by 50% from 12m to 6 min.
4. The image can now be built locally and pushed to the kind-registry for faster testing of a new faas-netes image.
5. Add load testing script in contrib/load_test.sh which currently requires hey.

Motivation and Context

• An issue has been raised to propose this change (required)

How Has This Been Tested?

• The CI job passes with a new image
• The create_dev.sh script works now

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.

[matzhaugen]

The build was building twice for each push so I removed this. I can put it back in if you want.