Fix Helm chart workflow action policy

[razinbouzar]

This PR replaces the Helm chart publishing workflow added in PR #26 with a publishing mechanism that works with Apache repository constraints.

The first workflow failed at startup because Apache's GitHub Actions policy blocks azure/setup-helm@v4. No chart artifacts were published.

We should keep the same public Helm repo contract:

https://apache.github.io/druid-operator

Expected gh-pages layout:

index.yaml
helm-releases/druid-operator-<version>.tgz

PR #27 already cleaned gh-pages, so this PR should only update how charts are published going forward.

Validation before publishing:

make helm-lint
make helm-template
make helm-package
make rat

Validation after publishing:

curl -I https://apache.github.io/druid-operator/index.yaml
helm repo add apache-druid https://apache.github.io/druid-operator
helm repo update
helm search repo apache-druid/druid-operator

Fixes #XXXX.

Description

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This PR has:

• been tested on a real K8S cluster to ensure creation of a brand new Druid cluster works.
• been tested for backward compatibility on a real K*S cluster by applying the changes introduced here on an existing Druid cluster. If there are any backward incompatible changes then they have been noted in the PR description.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

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Key changed/added files in this PR

• MyFoo
• OurBar
• TheirBaz