Prevent DefVar opcode emit for global binding

[HalidOdat]

No description provided.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	95,609	95,609	0
Passed	76,518	76,518	0
Ignored	18,132	18,132	0
Failed	959	959	0
Panics	0	0	0
Conformance	80.03%	80.03%	0.00%

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (34d5c51) 44.81% compared to head (64f6e84) 44.79%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3453      +/-   ##
==========================================
- Coverage   44.81%   44.79%   -0.02%     
==========================================
  Files         488      488              
  Lines       50373    50373              
==========================================
- Hits        22576    22567       -9     
- Misses      27797    27806       +9     

Files	Coverage Δ
boa_engine/src/bytecompiler/mod.rs	67.67% <33.33%> (-0.37%)	⬇️
boa_engine/src/vm/opcode/define/mod.rs	33.33% <0.00%> (-9.53%)	⬇️

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