Group helper functions by type

[JustinDrake]

Suggest grouping helpers in four categories:

1. Math and crypto
2. Non-boolean pure functions (get_...)
3. Boolean pure functions (is_...)
4. State-modifying functions

I have done the following renamings:

• get_epoch_start_slot => get_start_slot
• get_beacon_proposer_index => get_proposer_index
• bls_domain => get_bls_domain
• generate_seed => get_seed
• compute_committee => get_committee
• convert_to_indexed => get_indexed_attestation
• slot_to_epoch => get_epoch_from_slot
• verify_bitfield => is_valid_bitfield
• validate_indexed_attestation => is_valid_indexed_attestation
• get_shuffled_index => shuffle_index

Math

int_to_bytes
bytes_to_int
integer_squareroot
xor

Crypto

hash
hash_tree_root
signing_root
verify_merkle_branch
bls_verify
bls_verify_multiple
bls_aggregate_pubkeys

Non-boolean pure functions (get_...)

get_previous_epoch
get_current_epoch
get_start_slot
get_start_shard
get_epoch_from_slot
get_active_validator_indices
get_epoch_committee_count
get_shard_delta
get_crosslink_committee
get_block_root
get_randao_mix
get_seed
get_proposer_index
get_total_balance
get_churn_limit
get_delayed_activation_exit_epoch
get_crosslink_committee_for_attestation
get_attestation_participants
get_domain

Boolean pure functions (is_...)

is_active_validator
is_slashable_validator
is_double_vote
is_surround_vote
is_valid_bitfield
is_valid_indexed_attestation

State-modifying functions

activate_validator
initiate_validator_exit
slash_validator
set_balance
increase_balance
decrease_balance

[djrtwo]

I think this is reasonable.

[ralexstokes]

my two dai:

1. a nicer name for boolean pure functions could be predicates
2. consider the cost of losing semantic intent while pursuing uniformity, cf. compute_committee => get_committee, generate_seed => get_seed

i could easily be out-weighed here but ime get_foo has the connotation that you are just "chasing pointers" to get to some other data, with less, rather than more, computation along the way

[JustinDrake]

Mostly addressed in #1237 🎉