[SanderMuller]

Closes phpstan/phpstan#15620

An unpacked arg passes one value per item of its array. array_map() and immediately invoked closures typed it as one value. So the callback parameters and the return type of array_map() were wrong, and unpacking a general array reported a false argument.type error.

The new UnpackedArgumentTypes::expand() turns the arg types into one type per position:

• A list shape gives one type per required item. With a union of shapes, each position gets the union of the members, up to the smallest number of required items. The items after that go into a rest type.
• A general array, or a shape that is not a list, gives a rest type, because the number of values is not known.

These places use it:

• ContextualClosureParameterResolver, for array_map() callbacks and immediately invoked closures. A rest type becomes a variadic parameter.
• ParametersAcceptorSelector and ArrayMapParameterClosureTypeExtension. With a rest type, the callback keeps the type from the signature.
• ArrayMapFunctionReturnTypeExtension. With a rest type, it returns the declared type.

When the expansion gives a known number of arrays, array_map() now adds null for the shorter arrays. #6874 does the same for arrays that are not unpacked, but it skipped unpacked args.

ContextualClosureParameterResolver and ParametersAcceptorSelector have Turbo twins. Both C++ twins call the PHP helper.

Reproducer from the issue, at level 8:

Line	Before	After
9	array{4, 5, 6}	4|5|6
13	array{1, 2}	1
16	non-empty-list<array{4, 5, 6}>	non-empty-list<4|5|6>
18	Parameter #1 $callback of function array_map expects (callable(): mixed)|null, Closure(int, int): int given.	no error

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