Tidying up a few core functions

[terencechain]

What type of PR is this?

Feature

What does this PR do? Why is it needed?
Further clean ups for #6986 and #6983. There's no functionality changes. Just deletion and renaming:

• Removed ProcessVoluntaryExitsNoVerify. It was only used for tests
• Renamed ProcessVoluntaryExitsNoVerify to ProcessVoluntaryExitsNoVerifySignature
• Renamed ProcessAttestationNoVerify to ProcessAttestationNoVerifySignature
• Renamed VerifyAttestation to VerifyAttestationSignature. It makes the following b2b code more clear

Which issues(s) does this PR fix?

Fixes #

Other notes for review
CC @nisdas

[codecov]

Codecov Report

Merging #6995 into master will increase coverage by 2.34%.
The diff coverage is 72.39%.

@@            Coverage Diff             @@
##           master    #6995      +/-   ##
==========================================
+ Coverage   60.07%   62.41%   +2.34%     
==========================================
  Files         323      402      +79     
  Lines       27422    31895    +4473     
==========================================
+ Hits        16473    19907    +3434     
- Misses       8733     9185     +452     
- Partials     2216     2803     +587     

[nisdas]

I think we need to keep the voluntary exits(no verify), it is used for fuzzing that method. Otherwise with BLS the fuzzer will constantly fail.

[terencechain]

I think we need to keep the voluntary exits(no verify), it is used for fuzzing that method. Otherwise with BLS the fuzzer will constantly fail.

I dont think we still use beacon fuzz do we? We switched to cluster fuzz.

cc @prestonvanloon to confirm