Allow specifying human-readable duration string for drain timeout

[tongpu]

Is your feature request related to a problem? Please describe.

The drain timeout parameter in ManagedOSImage currently has to be configured in nanoseconds, which results in a lot of 0s in our YAML file.

Describe the solution you'd like Release v0.16.3 of the system-upgrade-controller allows specifying the drain timeout human units (e.g. 5m for 5 minutes) and this would be a usability improvement in the elemental-operator as well. By updating the dependency the CRD would be updated and allow human units in elemental-operator as well.

Additional context https://github.com/rancher/system-upgrade-controller/pull/379