[Refactor] Use Token Factory Method

[Alexius-Huang]

While inspecting the code in lexer, I noticed that the newToken method in lexer file violates the DRY rule. Thus, I come up with a way to change the token creation logic back to the token declaration file.

I'm not sure if there is a better approach, but overall, I hope this PR can help:

• Improve readability, follow DRY principle
• Token creation logic should be placed to where tokens are declared

[codecov[bot]]

Codecov Report

Merging #793 into master will decrease coverage by 0.01%. The diff coverage is 87.5%.

@@            Coverage Diff            @@
##           master    #793      +/-   ##
=========================================
- Coverage   80.31%   80.3%   -0.02%     
=========================================
  Files          54      54              
  Lines        7431    7417      -14     
=========================================
- Hits         5968    5956      -12     
+ Misses       1236    1234       -2     
  Partials      227     227

Impacted Files	Coverage Δ
compiler/token/token.go	100% <100%> (ø)	:arrow_up:
compiler/parser/expression_parsing.go	70% <60%> (+0.49%)	:arrow_up:
compiler/lexer/lexer.go	94.87% <87.09%> (-0.4%)	:arrow_down:

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[st0012]

@Maxwell-Alexius nice work! thanks 😄