add testcase for readany

[AllenX2018]

Add unit test for iterator.ReadAny() function.

[codecov]

Codecov Report

Merging #437 into master will decrease coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #437      +/-   ##
==========================================
- Coverage   86.85%   86.58%   -0.28%     
==========================================
  Files          41       41              
  Lines        5106     5106              
==========================================
- Hits         4435     4421      -14     
- Misses        535      549      +14     
  Partials      136      136

Impacted Files	Coverage Δ
reflect_struct_decoder.go	81.89% <0%> (-2.14%)	⬇️
any.go	81.25% <0%> (+1.04%)	⬆️

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