state: drop NativeContract, fix #3430

[roman-khimov]

This is somewhat deeper than its C# counterpart, but the essence is the same, we return proper []state.Contract from getnativecontracts RPC and thus many of older types are no longer needed. Some hacks around UpdateCounter are removed as well.

The change can potentially affect third-party apps, but should be easy to adopt.

UPD: simplified.

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 86.15%. Comparing base (13020cc) to head (b1bb12d).
Report is 6 commits behind head on master.

Files	Patch %	Lines
pkg/core/blockchain.go	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3439      +/-   ##
==========================================
+ Coverage   86.14%   86.15%   +0.01%     
==========================================
  Files         331      331              
  Lines       38432    38441       +9     
==========================================
+ Hits        33106    33120      +14     
+ Misses       3800     3797       -3     
+ Partials     1526     1524       -2     

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[AnnaShaleva]

To be honest, I'm against of ContractBase removal. NativeContract can be removed, but not the ContractBase. ContractBase is a separate type which should not include update counter. It's used by HFSpecificContractMD which should not be aware of the contract's update counter, and update counter is a kind of Management-specific and dao-specific thing that I'd like to keep inside Management.

[roman-khimov]

ContractBase removal

But the only reason we have it that there was this separation of native/non-native contract state. e1d2a5b.

[AnnaShaleva]

the only reason we have it that there was this separation

But right now it's not the only reason, because ContractBase is used by HFSpecificContractMD, and this entity is update-counter-agnostic.

[roman-khimov]

ContractBase is used by HFSpecificContractMD, and this entity is update-counter-agnostic.

I still think we have a lot to improve in HF handling. But OK, I'll simplify this to fix getnativecontracts only.

[AnnaShaleva]

I'm not completely against of ContractBase removal, but this code just doesn't work correctly.