feat: separate helm chart for CRDs

[mariuskimmina]

Closes #505
Supersedes #506

This is a first draft for a new helm chart k6-crds.

https://helm.sh/docs/chart_best_practices/custom_resource_definitions/#method-2-separate-charts

Examples of other projects following this approach:

• Karpenter https://github.com/aws/karpenter-provider-aws/tree/main/charts/karpenter-crd
• Prometheus Operator https://github.com/prometheus-community/helm-charts/tree/main/charts/prometheus-operator-crds

The current approach of having of having the CRDs defined under templates/crds is not a recommended pattern by helm. We could move CRDs to a dedicated /crds/ folder but as seen in #506 that creates it's own problems due to a lack of templating.

So far I liked the approach of having a separate chart for CRDs whenever I encountered it.

I think we can do this in two steps

1. Create the new k6-crds chart (this PR).
2. Remove the CRDs from k6-operator chart and add k6-crds chart as a dependency.

Converting to Draft as I didn't get to testing this yet.

[mariuskimmina]

Note: might want to wait for #500 and not include the k6 CRD here

[mariuskimmina]

Tested it now and it seems to be working fine.

I tested on a simple kind cluster by first installing the CRDs chart

helm install k6-crds ./k6-crds -n k6-testing 

Then installing removing the crds directory from the operator chart and running

helm install k6-operator ./k6-operator -n k6-testing

I then created a very minimal TestRun

apiVersion: k6.io/v1alpha1
kind: TestRun
metadata:
  name: k6-sample
  namespace: k6-testing
spec:
  parallelism: 1
  script:
    configMap:
      name: k6-test
      file: test.js
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: k6-test
  namespace: k6-testing
data:
  test.js: |
    import http from 'k6/http';
    import { sleep } from 'k6';

    export default function () {
      http.get('http://httpbin.org/get');
      sleep(1);
    }

All of this worked so I am going to mark this as ready for review now