Incomplete BLS key validation

[veorq]

Public key validation is done like this in the experimental Eth2 branch:

trinity/eth2/_utils/bls/validation.py

Lines 17 to 23 in 6813028

	def validate_public_key(pubkey: BLSPubkey, allow_empty: bool = False) -> None:
	if len(pubkey) != 48:
	raise PublicKeyError(
	f"Invalid public key length, expect 48 got {len(pubkey)}. pubkey: {pubkey.hex()}"
	)
	if not allow_empty and pubkey == EMPTY_PUBKEY:
	raise PublicKeyError(f"Empty public key is invalid pubkey={pubkey.hex()}")

It should include group membership and infinity checks, as per https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-04#section-2.5.