✨ CAPO v1beta2 API improvements

[nikParasyr]

/kind feature
/assign

This is the umbrella issue to keep track of API changes that we want to introduce in CAPO v1beta2.
Implementation of the changes will be after #2895 is done.

API changes:

• ✨ v1beta2: Standardize flavor in OpenStackMachine
• ✨ v1beta2: Add managedNetworks on OpenStackCluster
• ✨ v1beta2: Add managedRouters on OpenStackCluster
• ✨ v1beta2 Group apiServer related fields on OpenStackCluster
• ✨ v1beta2: Switch to positive polarity for bool fields in OpenStackCluster
• ✨ v1beta2: Rename allNodesSecurityGroupRules to indicate that it only applies for control-plane/worker nodes