Type Alias ErasValidatorPrefs

ErasValidatorPrefs: StorageDescriptor<
    [number, SS58String],
    { blocked: boolean; commission: number },
    false,
    never,
>

Similar to ErasStakers, this holds the preferences of validators.

This is keyed first by the era index to allow bulk deletion and then the stash account.

Is it removed after [Config::HistoryDepth] eras.