more BLS operations

[arvidn]

add negate, scalar_multiply, hash_to_g1, from_integer to point types as well as hash_to_g2.

These operations are sufficient to make clvm_rs use this crate instead of bls12_381

[coveralls-official]

Pull Request Test Coverage Report for Build 6183068964

• 272 of 333 (81.68%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 90.764%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
chia-bls/src/public_key.rs	154	162	95.06%
chia-bls/src/signature.rs	118	171	69.01%

Totals
Change from base Build 6113022885:	-0.3%
Covered Lines:	8835
Relevant Lines:	9734

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💛 - Coveralls

[arvidn]

it turns out there's some missing test coverage, especially of aggregate_pairing, but also some other failure cases. I'll add that before landing