fix: enable fuzz tests and fix decoder bugs

[liuq19]

1. Disable testing invalid UTF-8 in fuzzing.
2. Fixed some bugs found in fuzzing.

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (66bd218) 61.78% compared to head (850c83f) 61.78%.

Files	Patch %	Lines
dev/decoder/structs.go	0.00%	2 Missing ⚠️
dev/decoder/functor.go	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@               Coverage Diff                @@
##           test/aarch64     #597      +/-   ##
================================================
- Coverage         61.78%   61.78%   -0.01%     
================================================
  Files                84       84              
  Lines             10345    10342       -3     
================================================
- Hits               6392     6390       -2     
+ Misses             3569     3567       -2     
- Partials            384      385       +1     

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