Prune collected shared shapes

[HalidOdat]

This PR prunes all transitions in a SharedShape when a transition's WeakGc has been garbage collected and when we insert 255 properties/prototypes.

Example with debug print on prune:

>> ({a: 1})
{
   a: 1
}
>> ({a: 1, b: 2})
{
   a: 1,
   b: 2
}
>> $boa.gc.collect() // Trigger a garbage collection.
undefined
>> ({a: 1})
DEBUG PRINT - Pruning property transitions
{
   a: 1
}
>>

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	93,982	93,982	0
Passed	73,783	73,783	0
Ignored	17,489	17,489	0
Failed	2,710	2,710	0
Panics	0	0	0
Conformance	78.51%	78.51%	0.00%

[codecov]

Codecov Report

Merging #2941 (e2b203b) into main (4a368a2) will increase coverage by 0.03%.
The diff coverage is 80.85%.

@@            Coverage Diff             @@
##             main    #2941      +/-   ##
==========================================
+ Coverage   50.39%   50.42%   +0.03%     
==========================================
  Files         443      444       +1     
  Lines       45337    45392      +55     
==========================================
+ Hits        22846    22889      +43     
- Misses      22491    22503      +12     

Impacted Files	Coverage Δ
boa_engine/src/object/shape/shared_shape/mod.rs	84.15% <33.33%> (-0.85%)	⬇️
...rc/object/shape/shared_shape/forward_transition.rs	86.53% <81.57%> (-13.47%)	⬇️
boa_gc/src/pointers/ephemeron.rs	92.98% <100.00%> (+0.52%)	⬆️
boa_gc/src/pointers/weak.rs	70.58% <100.00%> (+3.92%)	⬆️

... and 10 files with indirect coverage changes

[raskad]

Do you think it makes sense to have a test for this behaviour?

[HalidOdat]

Do you think it makes sense to have a test for this behaviour?

will try to add the tests, and documentation on the two prune trigger methods :)

[raskad]

Really nice improvement!

[jedel1043]

LGTM!