vm_arm: add priority in vm config struct

[axel-h]

Adds the priorities to the vm config struct from the template. Is also makes VM_INIT_DEF use 100 as default base priority, so there is no need to explicitly specify anything. It also support the _priority. However, I wonder if we should clean this up an rename it to ìrqserver_prio`in the attribute also in a follow-up task

[hlyytine]

Also, shouldn't you get rid of hard coded value at https://github.com/seL4/camkes-vm/blob/ce598e47ef9df054e2d160bdd3fd51af07672686/components/VM_Arm/vm_common.camkes#L33 (and the other one on line 35 also)?

[axel-h]

Also, shouldn't you get rid of hard coded value at camkes-vm/components/VM_Arm/vm_common.camkes

Yes, seems this can also be removed then.