Added TryMarshalUnmarshal for fuzzers

[sirzooro]

Fuzzers need some public function to perform their work.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 81.20%. Comparing base (553d34c) to head (d73e46d).

Files	Patch %	Lines
packet.go	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #340      +/-   ##
==========================================
- Coverage   81.48%   81.20%   -0.28%     
==========================================
  Files          51       51              
  Lines        3327     3336       +9     
==========================================
- Hits         2711     2709       -2     
- Misses        471      481      +10     
- Partials      145      146       +1     

Flag	Coverage Δ
go	81.20% <0.00%> (-0.28%)	⬇️
wasm	67.41% <0.00%> (-0.19%)	⬇️

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