Merge Kubernetes Operator PR - Helm chart deprecation plan

[adutra]

Hi Nessie community,

As you may know, we have been working on a Nessie Operator for Kubernetes for quite a while now, and
we have a PR open for that. The PR has been reviewed by some folks already, and is ready to be
merged:

#7967

In the meantime, the Nessie Helm chart has received many updates.

Maintaining both the Helm chart and the Operator is a lot of work; besides, the complexity of the
Helm chart has increased significantly with the introduction of Iceberg REST Catalog support, to
the point that the templating logic is getting hard to maintain and error-prone.

Therefore, we would like to deprecate the Helm chart in favor of the Operator, as the Operator is
more flexible and provides a better user experience. It also has a much better test coverage than
the Helm chart.

But we understand that some users may still prefer the Helm chart, so we would like to ask the
community for feedback on this decision.

Our plan would be as follows:

1. Merge the Operator PR and release it as part of the next Nessie release. The Operator release
   would be marked as alpha initially, and would stay in alpha state for a while to gather feedback.

2. Mark the Helm chart as being in maintenance mode in the next Nessie release. As long as the
   Operator is in alpha, we would still maintain the Helm chart, including bug fixes and security
   updates, but we would not add new features to it.

3. Once the Operator reaches a stable release, we would deprecate the Helm chart and stop
   maintaining it.

Please let us know your thoughts on this plan. If you have any concerns or objections, please let us
know as well, either here, in the PR mentioned above, or in the Nessie Zulip
chat.