ValidatorGroups: StorageDescriptor<[], number[][], false, never>

All the validator groups. One for each core. Indices are into ActiveValidators - not the broader set of Polkadot validators, but instead just the subset used for parachains during this session.

Bound: The number of cores is the sum of the numbers of parachains and parathread multiplexers. Reasonably, 100-1000. The dominant factor is the number of validators: safe upper bound at 10k.