fix(validation): fix false-positive unresolved generic symbol validation for formal parameters

[mhasel]

When validating generic type-natures, we did not account for Identifier statements in formal parameter calls FOO(x := 0);, which will have a datatype that might look like the following example:

name: "__FOO__T",
    initial_value: None,
    information: Generic {
        name: "__FOO__T",
        generic_symbol: "T",
        nature: Num,
    },
    ...

and therefore be falsely validated as unresolved generic symbols. This PR adds an exception for Identifier statements during the type-nature validation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7e2e61a) 95.82% compared to head (13daff2) 95.83%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1066      +/-   ##
==========================================
+ Coverage   95.82%   95.83%   +0.01%     
==========================================
  Files         153      153              
  Lines       42806    42808       +2     
==========================================
+ Hits        41018    41026       +8     
+ Misses       1788     1782       -6     

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[volsa]

Weird, I don't get this message when running the example locally

[volsa]

Looks good 👍