Fix class constructor return value

[raskad]

This Pull Request changes the following:

• Adjust compilation of class constructors to always leave the stack with one return value.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	94,108	94,108	0
Passed	74,648	74,654	+6
Ignored	17,740	17,740	0
Failed	1,720	1,714	-6
Panics	0	0	0
Conformance	79.32%	79.33%	+0.01%

Fixed tests (6):

test/language/statements/class/poisoned-underscore-proto.js [strict mode] (previously Failed)
test/language/statements/class/poisoned-underscore-proto.js (previously Failed)
test/language/expressions/super/call-poisoned-underscore-proto.js [strict mode] (previously Failed)
test/language/expressions/super/call-poisoned-underscore-proto.js (previously Failed)
test/language/expressions/class/poisoned-underscore-proto.js [strict mode] (previously Failed)
test/language/expressions/class/poisoned-underscore-proto.js (previously Failed)

[codecov]

Codecov Report

Merging #3028 (79dc4f3) into main (423f099) will decrease coverage by 0.01%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##             main    #3028      +/-   ##
==========================================
- Coverage   50.56%   50.56%   -0.01%     
==========================================
  Files         446      446              
  Lines       45981    45983       +2     
==========================================
  Hits        23252    23252              
- Misses      22729    22731       +2     

Impacted Files	Coverage Δ
boa_engine/src/bytecompiler/class.rs	15.52% <33.33%> (-0.09%)	⬇️

[HalidOdat]

Nice catch! :)