AVM: Reorganize the crypto opcodes a bit to simplify incentive work

[jannotti]

Improves type checking a bit, improves ease of unit tests for new opcodes, moves crypto into their own files, adds some coverage.

[codecov]

Codecov Report

Merging #5787 (0fcda56) into master (6c482ab) will increase coverage by 0.03%.
The diff coverage is 87.43%.

@@            Coverage Diff             @@
##           master    #5787      +/-   ##
==========================================
+ Coverage   55.55%   55.58%   +0.03%     
==========================================
  Files         474      475       +1     
  Lines       66850    66850              
==========================================
+ Hits        37138    37161      +23     
+ Misses      27188    27180       -8     
+ Partials     2524     2509      -15     

Files	Coverage Δ
crypto/onetimesig.go	76.15% <ø> (ø)
data/transactions/logic/doc.go	70.96% <ø> (ø)
data/transactions/logic/eval.go	92.85% <ø> (+0.54%)	⬆️
data/transactions/logic/opcodes.go	79.84% <ø> (ø)
data/transactions/logic/crypto.go	87.43% <87.43%> (ø)

... and 16 files with indirect coverage changes

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[jasonpaulos]

Looks mostly good, I just have some minor questions/comments.

I also verified the new crypto.go contains exactly the code removed from eval.go

[algorandskiy]

LGTM, one question about a newly added notrack below