Move functions from helpers.py to committee_helpers.py and epoch_processing_helpers.py

[hwwhww]

What was wrong?

Too many functions in helpers.py, and the test_helpers.py is getting longer and longer.

How was it fixed?

No logic changes in this PR.

• For the functions for shuffling, find the proposer ... this kind of functions are related to committee shuffling, move them to committee_helpers.py.
• For the functions that defined in https://github.com/ethereum/eth2.0-specs/blob/dev/specs/core/0_beacon-chain.md#helpers, move them to epoch_processing_helpers.py.

Note the dependencies are:

• committee_helpers.py depends on helper.py.
• epoch_processing_helpers depends on helper.py and committee_helpers.py.

/cc @pipermerriam @djrtwo @ChihChengLiang @NIC619 @jannikluhn

Any objection to this reorg? If no, I will continue to reorg test_helpers.py too.

Other thoughts on the file path reorg:

1. There may be another new category attestation_helpers.py for the helper functions that related to Attestation and SlashableAttestation, but I'm inclined to leave it after Remove placeholder #250 and other in-progressing PR merged.
2. We can move all the _helpers.py files into helpers folder, and remove the suffix.

Cute Animal Picture

[djrtwo]

reorg lgtm

[pipermerriam]

2. We can move all the `_helpers.py` files into `helpers` folder, and remove the suffix.

👍

• helpers.attestations
• helpers.committee

That makes a lot more sense to me than suffixing.

[pipermerriam]

Rubber stamp on the conceptual re-org. didn't actually browse the details of the diff.