Normalize attestation signature getter name

[djrtwo]

Supersedes #1670

• based on v011x branch for inclusion in coming release
• cherry-picked @arnetheduck's commit from Normalize attestation signature getter name #1670
• minor mod to naming for clarity

[hwwhww]

LGTM!

[arnetheduck]

fwiw, in the code we ended up with a bunch of these get_*_signature - they work with minimal information though and not the full state - effectively, we don't want to send the whole state across to the validator, so we pick the specific data:

https://github.com/status-im/nim-beacon-chain/blob/a7963b0b8c9113466dc4dabce62a193b00d228f0/beacon_chain/spec/state_transition_block.nim#L485

[djrtwo]

The decision to pass the state around around most times was to reduce the size of crazy function signatures (some that would have 8+ args). That decision rippled through the entire codebase for better or worse.

Much respect for your functions