Allow iterators of unknown size in macros

[odow]

Closes #1915

[codecov]

Codecov Report

Merging #2550 (591c63a) into master (54c3c2c) will increase coverage by 0.19%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2550      +/-   ##
==========================================
+ Coverage   92.94%   93.13%   +0.19%     
==========================================
  Files          44       44              
  Lines        5457     5481      +24     
==========================================
+ Hits         5072     5105      +33     
+ Misses        385      376       -9     

Impacted Files	Coverage Δ
src/Containers/vectorized_product_iterator.jl	76.19% <100.00%> (+7.44%)	⬆️
src/Containers/DenseAxisArray.jl	88.33% <0.00%> (+1.18%)	⬆️
src/parse_nlp.jl	95.50% <0.00%> (+4.29%)	⬆️

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