Make tests 🥑

[ChunyiLyu]

This closes #446

Note to reviewers: remember to look at the commits in this PR and consider if they can be squashed

Summary Of Changes

• Added new make targets: make chart-tests, make kubectl-plugin-tests, and make tests which runs unit, integration, system, chart, and plugin tests

• Use these new make target in PR workflow

Additional Context

Local Testing

Please ensure you run the unit, integration and system tests before approving the PR.

To run the unit and integration tests:

$ make unit-tests integration-tests

You will need to target a k8s cluster and have the operator deployed for running the system tests.

For example, for a Kubernetes context named dev-bunny:

$ kubectx dev-bunny
$ make destroy deploy-dev
# wait for operator to be deployed
$ make system-tests

[Zerpet]

The errors in the checks seem legitimate. The containers in GitHub Actions may not have all the tools we have in our dev machines.

[ChunyiLyu]

@Zerpet Indeed. I'm not sure how it was passing before, but the error is because the container does not have krew installed. Going to fix it now.

[coro]

Hooray!