[gardener-extension-shoot-dns-service]

Improvements

• [OPERATOR] fixing panic on deleting multiple DNS entries from state (#22, @MartinWeindel)
• [OPERATOR] Use caching kubernetes client with partial disabled cache (#20, @MartinWeindel)
• [OPERATOR] Several controller options have been made available to operators via CLI and the containing Helm chart: lifecycle-max-concurrent-reconciles, healthcheck-max-concurrent-reconciles, replication-max-concurrent-reconciles (#19, @timuthy)