fix: refactor error handling

[yunwei37]

Description

• use neexcept for all vm functions
• remove exit on error

[codecov]

Codecov Report

Attention: Patch coverage is 85.21127% with 21 lines in your changes missing coverage. Please review.

Project coverage is 78.34%. Comparing base (f6a726c) to head (19010b6).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/vm.cpp	62.85%	13 Missing ⚠️
src/llvm_jit_context.cpp	72.41%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
+ Coverage   75.96%   78.34%   +2.38%     
==========================================
  Files           9       10       +1     
  Lines        1040     1136      +96     
  Branches      105      115      +10     
==========================================
+ Hits          790      890     +100     
+ Misses        250      246       -4     

Flag	Coverage Δ
bpf_conformance	61.61% <15.49%> (-4.73%)	⬇️
unittests	51.01% <85.21%> (+4.91%)	⬆️

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