feat: add support for constants in imported modules

[charles-cooper]

What I did

allow importing constants from modules

How I did it

add a case to ConstantFolder, and move the constant folder slightly down in the pipeline to after imports have been resolved.

How to verify it

see tests

Commit message

feat: add support for constants in imported modules

- add a case to ConstantFolder, and move the constant folder slightly
  down in the pipeline to after imports have been resolved.
- rename `pre_typecheck` to `constant_fold` (since that is all it does,
  and it doesn't strictly happen before typechecking anymore).

Description for the changelog

Cute Animal Picture

[pcaversaccio]

Can we additionally fuzz the input types for the constant values in tests? The unit tests & the overall PR lgtm (besides the open errors) but this would be a great case IMO to parametrise the (allowed) types for a fuzz test.

[charles-cooper]

Can we additionally fuzz the input types for the constant values in tests? The unit tests & the overall PR lgtm (besides the open errors) but this would be a great case IMO to parametrise the (allowed) types for a fuzz test.

added a test for arrays -- 251de24

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5c2177b) 84.16% compared to head (251de24) 84.21%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3726      +/-   ##
==========================================
+ Coverage   84.16%   84.21%   +0.05%     
==========================================
  Files          92       92              
  Lines       13119    13137      +18     
  Branches     2925     2928       +3     
==========================================
+ Hits        11041    11063      +22     
+ Misses       1659     1655       -4     
  Partials      419      419              

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[charles-cooper]

the docs failure is unrelated; fixed here: #3728