Deprecate incrementing `version` in values.yaml for every commit?

Our [contributing guidelines](https://github.com/cockroachdb/helm-charts/blob/master/cockroachdb/CONTRIBUTING.md) require that every commit increment the `version` field in `values.yaml`. This is easy to forget, and is also a frequent source of merge conflicts.

It should be possible to only require incrementing the `version` field for backwards-incompatible changes. For minor changes which are backwards-compatible, a minor version could be generated automatically post-commit.

Jira issue: HELM-40

Read cockroachdb/CONTRIBUTING.md and the chart's values.yaml to confirm the current versioning requirement. Review how chart changes and releases are handled; done means an agreed, documented approach that avoids manual increments for backward-compatible changes while preserving them for incompatible changes.

Written by the indexing model from the issue text.