Refactor syscall handing

[fyrchik]

Depends on #1711 .

1. Introduce neogointernal package with Syscall* functions.
2. Process syscall wrappers as usual Go functions.
3. For native contract wrappers inlinining is done twice (for the func itself + inner syscall).

[codecov]

Codecov Report

Merging #1720 (8511825) into master (abee3b5) will decrease coverage by 0.10%.
The diff coverage is 31.94%.

@@            Coverage Diff             @@
##           master    #1720      +/-   ##
==========================================
- Coverage   82.71%   82.61%   -0.11%     
==========================================
  Files         270      272       +2     
  Lines       22193    22157      -36     
==========================================
- Hits        18356    18304      -52     
- Misses       2712     2731      +19     
+ Partials     1125     1122       -3     

Impacted Files	Coverage Δ
pkg/interop/binary/binary.go	0.00% <0.00%> (ø)
pkg/interop/contract/contract.go	0.00% <0.00%> (ø)
pkg/interop/crypto/crypto.go	0.00% <0.00%> (ø)
pkg/interop/iterator/iterator.go	0.00% <0.00%> (ø)
pkg/interop/json/json.go	0.00% <0.00%> (ø)
pkg/interop/neogointernal/syscall.go	0.00% <0.00%> (ø)
pkg/interop/runtime/engine.go	0.00% <0.00%> (ø)
pkg/interop/runtime/runtime.go	0.00% <0.00%> (ø)
pkg/interop/storage/storage.go	0.00% <0.00%> (ø)
pkg/compiler/analysis.go	96.47% <100.00%> (-0.63%)	⬇️
... and 18 more

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[roman-khimov]

And it seems to be fixing #941, but it's not mentioned anywhere.