Refactor JSON generation process

[ ] All []byte types should be custom types that serialize to hex #278
[ ] GetPostState and WriteJsonStateComparison shouldn't use interface{}. https://github.com/bloxapp/ssv-spec/pull/281#discussion_r1253019248
[x] Remove * from folder names: https://github.com/bloxapp/ssv-spec/pull/281#discussion_r1250621170
[x] MultiMsgProcessingSpecTest should create a json file for each subtest
[ ] GetPostState has lots of copy pastes across different files. Try to make it better.
[ ] overrideStateComparison has lots of copy pastes across different files. Try to make it better.
[ ] Enable deletion of post-state root in test files
[ ] rename comparable package. https://github.com/bloxapp/ssv-spec/pull/286#discussion_r1260062019
[ ] #482

ssvlabs / ssv-spec