🎄 scparser: add helpers for basic types parsing 🎄

[AnnaShaleva]

TODO:

• SYSCALL parser.
• Unit tests.
• A couple of parsers for common use-cases.
• Doc examples.

[codecov]

Codecov Report

❌ Patch coverage is 13.69863% with 63 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.33%. Comparing base (6d157f6) to head (bd63b76).

Files with missing lines	Patch %	Lines
pkg/smartcontract/scparser/contract_checks.go	13.69%	61 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4122      +/-   ##
==========================================
- Coverage   83.50%   83.33%   -0.18%     
==========================================
  Files         353      353              
  Lines       42827    42890      +63     
==========================================
- Hits        35764    35741      -23     
- Misses       5305     5394      +89     
+ Partials     1758     1755       -3     

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