Simplify decoding compressed Y

[im-kulikov]

Step by step ops with comments

[codecov]

Codecov Report

Merging #447 into master will increase coverage by 0.02%.
The diff coverage is 90%.

@@            Coverage Diff             @@
##           master     #447      +/-   ##
==========================================
+ Coverage   48.22%   48.25%   +0.02%     
==========================================
  Files         103      103              
  Lines        7861     7859       -2     
==========================================
+ Hits         3791     3792       +1     
+ Misses       3764     3759       -5     
- Partials      306      308       +2

Impacted Files	Coverage Δ
pkg/crypto/keys/publickey.go	53.67% <90%> (-1.4%)	⬇️
pkg/core/blockchain.go	36.71% <0%> (+0.58%)	⬆️

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[roman-khimov]

I don't see how it improves anything, really. Adding comments would probably help, but rewriting it this way? Also, this code works and probably won't be touched for years, it's a very minor technical detail. Chances are it's even gonna be moved into golang itself: golang/go#34105.

[im-kulikov]

@roman-khimov I just replace code with code taken from stdlib, it's more clearly to understand IMHO

[roman-khimov]

I don't see much interest in this change and it's not obvious whether it improves anything, so I'm closing it.