Add Github actions that check Metal3 chart and validate all Edge PRs

[Kristian-ZH]

This PR adds two Github actions that aim to make a first level of validations that will verify that the chart is successfully deployed and that the Metal3 pods are running

1. Check that will be triggered on every PR that modifies the assets/metal3/metal3-0.2.0.tgz file. It will install the metal3 helm chart and will validate if all pods are running in a k3s cluster.
2. Check that will be triggered on every pr in the charts repo and will run make validate command

[hardys]

This is awesome, thanks @Kristian-ZH for working on this! 👍

A couple of minor comments, but this looks great and is an excellent first step towards enabling some functional tests.