A BLS pubkey aggregation combines a series of pubkeys into a single pubkey.
The test data is declared in a data.yaml file:
input: List[BLS Pubkey] -- list of input BLS pubkeys
output: BLS Pubkey -- expected output, single BLS pubkeyBLS Pubkey here is encoded as a string: hexadecimal encoding of 48 bytes (96 nibbles), prefixed with 0x.
The aggregate_pubkeys handler should aggregate the keys in the input, and the result should match the expected output.