provide builtin clone mechanism to replace reflection

[xushiwei]

#117

[codecov]

Codecov Report

Attention: Patch coverage is 61.90476% with 8 lines in your changes missing coverage. Please review.

Project coverage is 29.97%. Comparing base (955f8cb) to head (f723ec8).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
classfile_v2.go	75.00%	4 Missing ⚠️
context.go	33.33%	2 Missing ⚠️
yap.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #130      +/-   ##
==========================================
+ Coverage   22.34%   29.97%   +7.62%     
==========================================
  Files          10       10              
  Lines         962      964       +2     
==========================================
+ Hits          215      289      +74     
+ Misses        728      647      -81     
- Partials       19       28       +9     

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