refactor: Rename VarAD to ad.Num and delete VecAD

[samestep]

Description

Resolves #906 (comment) by renaming or deleting everything remaining in types/ad that had an AD suffix. Note that just like #907, this PR does not modify packages/docs-site/docs/ref/style/functions.mdx because #927 is not yet resolved.

This PR also renames two functions in engine/EngineUtils:

• valueVarADs -> valueADNums
• colorVarADs -> colorADNums

Checklist

• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new ESLint warnings
• I have reviewed any generated changes to the diagrams/ folder

[codecov]

Codecov Report

Merging #974 (a52b26a) into main (59cfdcf) will increase coverage by 0.04%.
The diff coverage is 68.48%.

@@            Coverage Diff             @@
##             main     #974      +/-   ##
==========================================
+ Coverage   63.41%   63.45%   +0.04%     
==========================================
  Files          62       62              
  Lines        7886     7895       +9     
  Branches     1827     1830       +3     
==========================================
+ Hits         5001     5010       +9     
  Misses       2766     2766              
  Partials      119      119              

Impacted Files	Coverage Δ
packages/core/src/renderer/Staging.ts	12.50% <0.00%> (ø)
packages/core/src/shapes/Circle.ts	100.00% <ø> (ø)
packages/core/src/shapes/Ellipse.ts	100.00% <ø> (ø)
packages/core/src/shapes/Line.ts	100.00% <ø> (ø)
packages/core/src/shapes/Path.ts	100.00% <ø> (ø)
packages/core/src/shapes/Shapes.ts	100.00% <ø> (ø)
packages/core/src/shapes/Text.ts	60.00% <ø> (ø)
packages/core/src/utils/toCustomAD.ts	88.27% <ø> (ø)
packages/core/src/contrib/Functions.ts	13.60% <16.16%> (ø)
packages/core/src/contrib/Objectives.ts	17.69% <40.00%> (ø)
... and 18 more

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