BUG: Fix npt.ArrayLike treating (builtin) scalar- and __array__-sequences as mutually exclusive

[BvB93]

cc @bashtage

npt.ArrayLike consists four components:

• Builtin scalar types
• __array__ implementation
• Nested sequences of builtins scalar types
• Nested sequences of __array__ implementation

The problem was that, previously, the latter two were considered mutually exclusive, e.g. list[list[int] | np.ndarray] was not considered a proper npt.ArrayLike subtype. This PR fixes aforementioned issue by shuffling around the relevant union a bit.

[charris]

There are test failures.

[BvB93]

There are test failures.

Yes, and the failure appears to be real...
Marking as draft for now until I've time to do some debugging.

[BvB93]

Closed in favor of #21102.

Based on the error message (see below), it would something this change causes list[str] to be recognized as a subtype of npt._ArrayLikeInt_co, thus causing the structured array to hit an overload-path intended for integer-based indexing.

The only reasonable explanation I can think of is that mypy hits some sort of recursion limit, causing str to be expanded to either Any or Sequence[Any]. With Any being Any, this would explain why a string is all of a sudden considered a "valid" integer subtype.

Error message

 __________________________ test_reveal[ndarray_misc] ___________________________

path = '/home/runner/work/numpy/numpy/venv-for-wheel/lib/python3.8/site-packages/numpy/typing/tests/data/reveal/ndarray_misc.pyi'
expression = 'reveal_type(AR_V[["a", "b"]])'
reveal = 'ndarray[Any, dtype[void]]'
expected_reveal = '209: note: Revealed type is "Any"', lineno = 209

    def _test_reveal(
        path: str,
        expression: str,
        reveal: str,
        expected_reveal: str,
        lineno: int,
    ) -> None:
        """Error-reporting helper function for `test_reveal`."""
        stripped_reveal = _STRIP_PATTERN.sub(strip_func, reveal)
        stripped_expected_reveal = _STRIP_PATTERN.sub(strip_func, expected_reveal)
        if stripped_reveal not in stripped_expected_reveal:
>           raise AssertionError(
                _REVEAL_MSG.format(lineno,
                                   expression,
                                   stripped_expected_reveal,
                                   stripped_reveal)
            )
E           AssertionError: Reveal mismatch at line 209
E           
E           Expression: reveal_type(AR_V[["a", "b"]])
E           Expected reveal: '209: note: Revealed type is "Any"'
E           Observed reveal: 'ndarray[Any, dtype[void]]'

expected_reveal = '209: note: Revealed type is "Any"'
expression = 'reveal_type(AR_V[["a", "b"]])'
lineno     = 209
path       = '/home/runner/work/numpy/numpy/venv-for-wheel/lib/python3.8/site-packages/numpy/typing/tests/data/reveal/ndarray_misc.pyi'
reveal     = 'ndarray[Any, dtype[void]]'
stripped_expected_reveal = '209: note: Revealed type is "Any"'
stripped_reveal = 'ndarray[Any, dtype[void]]'