Refactor parser for modularity

[gnikit]

Breaks the AST nodes of the parser into separate module files. Important to keep the code clean.

TODO:

• [ ] Increase converage
• [ ] Fix poor quality code Issues
• [ ] Simpligy certain parts of the AST nodes

[codecov[bot]]

Codecov Report

Attention: 254 lines in your changes are missing coverage. Please review.

Comparison is base (b06a833) 87.54% compared to head (df9f621) 87.51%.

Files	Patch %	Lines
fortls/parsers/internal/type.py	61.06%	44 Missing :warning:
fortls/parsers/internal/ast.py	86.19%	33 Missing :warning:
fortls/parsers/internal/subroutine.py	83.43%	28 Missing :warning:
fortls/parsers/internal/utilities.py	86.55%	25 Missing :warning:
fortls/parsers/internal/variable.py	84.41%	24 Missing :warning:
fortls/parsers/internal/scope.py	86.52%	19 Missing :warning:
fortls/parsers/internal/function.py	77.92%	17 Missing :warning:
fortls/parsers/internal/method.py	79.26%	17 Missing :warning:
fortls/parsers/internal/base.py	84.33%	13 Missing :warning:
fortls/parsers/internal/submodule.py	89.47%	8 Missing :warning:
... and 11 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #333 +/- ## ========================================== - Coverage 87.54% 87.51% -0.04% ========================================== Files 12 35 +23 Lines 4567 4756 +189 ========================================== + Hits 3998 4162 +164 - Misses 569 594 +25 ```

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[gnikit]

I have gone line by line-by-line through the newly created files and the coverage is identical (bar a +1 line coverage in the BLOCK AST node, function req_named_end).