Type Alias HrmpIngressChannelsIndex

HrmpIngressChannelsIndex: StorageDescriptor<
    [Key: number],
    number[],
    false,
    never,
>

Ingress/egress indexes allow to find all the senders and receivers given the opposite side. I.e.

(a) ingress index allows to find all the senders for a given recipient. (b) egress index allows to find all the recipients for a given sender.

Invariants:

for each ingress index entry for P each item I in the index should present in HrmpChannels as (I, P).
for each egress index entry for P each item E in the index should present in HrmpChannels as (P, E).
there should be no other dangling channels in HrmpChannels.
the vectors are sorted.