Improve downgrade array spread stability

[TomasVotruba]

In some cases we're unable to resolve keys propperly, as relying on docblocks. This can lead to bugs as rectorphp/rector#9448

To safeguard this, Rector will always downgrade array spread to array_merge() if going down to PHP 8.1 or 7.4.

[samsonasik]

While this fix the issue, the possible bug is the updated IntersectionType -> AccessoryArrayListType cleaning on your PR:

• Add array with dim fetch assign support to AddMethodCallBasedStrictParamTypeRector rector-src#7506

for multiple data, a[]&b[]&c[], this should be directly array return instead, so should be something like:

if ($intersectionType instanceof AccessoryArrayListType) {
       return new ArrayType(new MixedType(), new MixedType());
}