[bitnami/mlflow] Add support for Google Cloud Storage as artifact store

[mautini]

Description of the change

This PR follows this one https://github.com/bitnami/charts/pull/26461 and integration of google-cloud-storage library in bitnami mlflow Docker image: https://github.com/bitnami/containers/pull/67246

It adds support to Google Cloud Storage as backend store for mlflow artifacts. The use could specify credentials via workload identity or application credential.

Benefits

User will be able to use Google Storage as backend for artifact storage in mlflow tracking. This is useful for other that migrate from another mlflow instance (running with GCS as backend) or that cannot use other cloud provider.

Possible drawbacks

More complexity to the helm chart / configuration? But it's a feature supported by mlflow so I think we have to expose it.

Checklist

• [x] Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• [x] Variables are documented in the values.yaml and added to the README.md using readme-generator-for-helm
• [x] Title of the pull request follows this pattern [bitnami/<name_of_the_chart>] Descriptive title
• [x] All commits signed off and in agreement of Developer Certificate of Origin (DCO)