Choose HetznerBareMetalHosts with RootDeviceHints set over those ones without

[janiskemper]

/kind feature

Describe the solution you'd like
Currently, we choose the first HetznerBareMetalHost of the list that fits the criteria. This leads to the fact that a host might be chosen that does not have rootDeviceHints set. This is not a problem per se, as the user will get the necessary information printed in the status of HetznerBareMetalHost and can use it to specify the rootDeviceHints.

However, this is not optimal in the case where other HetznerBareMetalHosts are available that have the rootDeviceHints specified. The provisioning of those hosts is naturally faster than if the user has to do some manual work.

Therefore, I propose to choose those HetznerBareMetalHosts first that have the rootDeviceHints specified.