Add reference test for invalid deposit with unparsable public key

[ajsutton]

There doesn't appear to be any reference test that uses an unparsable public key in deposits. There's tests for invalid signatures but there are a few cases with public keys worth testing:

1. An unparsable public key e.g. 0x000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
2. The infinite public key 0xc00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
3. A public key that's not part of the g1 group

[ajsutton]

It's probably also worth testing these with a single deposit and with the full 16 deposits. It can be useful to use batch signature verification since deposit signatures are usually valid but if any are invalid you have to go find the right one (which can be complicated by things like unparseable public keys). One vs multiple deposits did wind up making a difference in Teku.

[Nashatyrev]

It probably makes sense to add other cases:
4. Point which is not on the curve
E.g.
0x800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
5. (Supranational Blst implementation specific case) Point which is on curve, not in G1 group, but is reported as invalid during point construction (without P1_affine.in_group() call)
0x800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

Also the sample for the case (3):
0x800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004

[Nashatyrev]

Related spec PR: #2987