Add a Helm Chart for deploying Solr Clouds

[HoustonPutman]

We currently have a Helm Chart to deploy the Solr Operator, but users still have to manually create yaml files for their clouds/collections/etc.

It would be great to have helm charts that allow for users to easily create new SolrClouds (with metrics or collections included possibly). That way creating a solr cloud is two calls maximum (one to install the operator via helm, one to install the cloud via helm).

[mogul]

Another reason for having a SolrCloud Helm chart is that it would be helpful in documenting all the available options (eg ingressOptions) which are not used in examples and tutorials, and which are not explicitly documented in the docs/ folder... Having a place where everything functional is overridden, as in a Helm template, will lead to that functional YAML stanza (presumably under test!) being the same as documentation.