[Feature] Fleet - customize resource group name

When using creating a Kubernetes fleet manager, it creates two additional RG, one FL_ for hosting the hub cluster and one FL_MC_ for hosting the resources of the hub.

**Describe the solution you'd like**
The same feature as --node-resource-group parameter, the capacity to specify the generated resource group name(s).

**Describe alternatives you've considered**
None and it's a real issue when the customer implements naming policies

something like. next question, do we need two resources groups ? why can't the hub either in the first one, or the MC one ?
`az fleet create --resource-group ${RESOURCE_GROUP} --name ${FLEET_NAME} --location westeurope --node-resource-group`