Support graceful shutdown

[sbernauer]

Part of stackabletech/issues#357

Must

• Code goes into rust/operator-binary/src/operations/graceful_shutdown.rs (if needed)
• Update docs/modules/<operator>/pages/usage-guide/operations/graceful-shutdown.adoc
• Functionality verified manually by restarting Pods
• Graceful shutdown period must be configurable, probably on roleGroup config (see CRD changes tab). Implementation is copied from trino-operator and uses human-readable time.
• Sane default for graceful shutdown period determined
• smoke test tests default value

Should

• Integration test added, e.g. something like chaos monkey in hdfs. This is probably the hardest part of the whole task, so it's a "Should"