Fix the array API unique_*() functions to not compare nans as equal

The spec requires this, but it is only now possible to implement with the new
equal_nan flag in np.unique().

Original NumPy Commit: 12f83eb7337b840e3cd9026779b99b1af8033bf3

Author: asmeurer

array_api_strict/_set_functions.py

@@ -46,6 +46,7 @@ def unique_all(x: Array, /) -> UniqueAllResult:
         return_counts=True,
         return_index=True,
         return_inverse=True,
+        equal_nan=False,
     )
     # np.unique() flattens inverse indices, but they need to share x's shape
     # See https://github.com/numpy/numpy/issues/20638
@@ -64,6 +65,7 @@ def unique_counts(x: Array, /) -> UniqueCountsResult:
         return_counts=True,
         return_index=False,
         return_inverse=False,
+        equal_nan=False,
     )
 
     return UniqueCountsResult(*[Array._new(i) for i in res])
@@ -80,6 +82,7 @@ def unique_inverse(x: Array, /) -> UniqueInverseResult:
         return_counts=False,
         return_index=False,
         return_inverse=True,
+        equal_nan=False,
     )
     # np.unique() flattens inverse indices, but they need to share x's shape
     # See https://github.com/numpy/numpy/issues/20638
@@ -98,5 +101,6 @@ def unique_values(x: Array, /) -> Array:
         return_counts=False,
         return_index=False,
         return_inverse=False,
+        equal_nan=False,
     )
     return Array._new(res)