Feat: Remove String type

[mrLSD]

Description

↪️ Implementation of #31

String type considerations

PromitiveTypes represents only the most primitive types.

As potential pitfalls for backend implementation, String type mostly represents a complex type. For examples:

• sized array[char]
• unsized array[u8]
• or other, including low-level LLVM representations.

✅ To avoid that collision, String type was removed from PromitiveTypes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.89%. Comparing base (76126a5) to head (e34402d).

Additional details and impacted files

@@             Coverage Diff             @@
##            master      #32      +/-   ##
===========================================
- Coverage   100.00%   99.89%   -0.11%     
===========================================
  Files            9        9              
  Lines         1964     1949      -15     
===========================================
- Hits          1964     1947      -17     
- Misses           0        2       +2     

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