native: emit vote/candidate events

[roman-khimov]

Follow neo-project/neo#2754.

I'll probably add some tests.

[codecov]

Codecov Report

Merging #2523 (5e01331) into master (c605cfb) will increase coverage by 0.09%.
The diff coverage is 90.64%.

@@            Coverage Diff             @@
##           master    #2523      +/-   ##
==========================================
+ Coverage   85.02%   85.12%   +0.09%     
==========================================
  Files         294      294              
  Lines       37005    37075      +70     
==========================================
+ Hits        31465    31560      +95     
+ Misses       4219     4189      -30     
- Partials     1321     1326       +5     

Impacted Files	Coverage Δ
pkg/vm/vm.go	94.14% <62.50%> (-0.40%)	⬇️
pkg/core/interop/contract/call.go	73.38% <80.00%> (+0.38%)	⬆️
pkg/core/blockchain.go	82.31% <100.00%> (ø)
pkg/core/interop/context.go	92.14% <100.00%> (+0.25%)	⬆️
pkg/core/interop/runtime/engine.go	100.00% <100.00%> (ø)
pkg/core/native/designate.go	82.18% <100.00%> (-0.29%)	⬇️
pkg/core/native/management.go	92.41% <100.00%> (-0.09%)	⬇️
pkg/core/native/native_neo.go	81.81% <100.00%> (+1.46%)	⬆️
pkg/core/native/native_nep17.go	87.20% <100.00%> (-0.26%)	⬇️
pkg/core/native/oracle.go	72.19% <100.00%> (-0.54%)	⬇️
... and 7 more

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