grandpa_authorities: RuntimeDescriptor<[], [FixedSizeBinary<32>, bigint][]>

Get the current GRANDPA authorities and weights. This should not change except for when changes are scheduled and the corresponding delay has passed.

When called at block B, it will return the set of authorities that should be used to finalize descendants of this block (B+1, B+2, ...). The block B itself is finalized by the authorities from block B-1.