the overall number of row/columns taken into custody by a node is determined by
a base number (custody) and a class specific multiplier (validatorsPerNode).
We support two models:
- validatorsBasedCustody: each validator has a unique subset of size custody,
and custody is the union of these. I.e. VPN is a "probabilistic multiplier"
- !validatorsBasedCustody: VPN is interpreted as a simple custody multiplier
Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>