Set the array "length" property in [[DefineOwnProperty]] based on the array shape

[raskad]

This optimization is especially useful for array literal construction. Instead of calling OrdinaryGetOwnProperty and OrdinaryDefineOwnProperty on the array object while setting the "length" property, all of that can be skipped if the shape of the array has not changed.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	48,625	48,625	0
Passed	43,947	43,947	0
Ignored	1,471	1,471	0
Failed	3,207	3,207	0
Panics	0	0	0
Conformance	90.38%	90.38%	0.00%

[raskad]

As you can see the Splay benchmark benefits a lot from this change, since it constructs an array literal during execution.

Before:

RESULT Richards 131
RESULT DeltaBlue 115
RESULT Crypto 120
RESULT RayTrace 277
RESULT EarleyBoyer 365
RESULT RegExp 64.1
RESULT Splay 525
RESULT NavierStokes 341
SCORE 195

After:

RESULT Richards 132
RESULT DeltaBlue 114
RESULT Crypto 118
RESULT RayTrace 276
RESULT EarleyBoyer 367
RESULT RegExp 62.5
RESULT Splay 672
RESULT NavierStokes 340
SCORE 200

[jedel1043]

Nice optimization!

[HalidOdat]

Looks perfect to me :)