remove special case for G1Element in SExp.to()

[arvidn]

Instead support any type that can convert to bytes.

[coveralls-official]

Pull Request Test Coverage Report for Build 5877680554

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.345%

---

Totals
Change from base Build 4176492396:	0.0%
Covered Lines:	916
Relevant Lines:	951

---

💛 - Coveralls

[richardkiss]

More general and better. My only concern is that the type signature for convert_atom_to_bytes no longer reflects that G1Element is safe, so may cause mypy problems. This isn't easy to fix unless we ignore py3.7, which is EOL June, 2023, so maybe it's okay. ChatGPT says we can do something like this:

from typing import Protocol, runtime_checkable

@runtime_checkable
class CanBeCastToBytes(Protocol):
    def __bytes__(self) -> bytes: ...

but it only works in 3.8+.

[arvidn]

yeah, as far as I can tell, in all situations we use this in chia-blockchain right now, the types of the list is erased already anyway. So in practice it's not a regression (yet). I suppose we would need to export a protocol that we could use in chia-blockchain as well, as the member of our List[x]