Closes gh-1135

Handle x[True] and x[False] as NumPy does, even though the behavior
may be undocumented. NumPy treats True as None (insert axis with size 1),
and treats False as None followed by empty slicing (insert axis with size 0).

Changed the logic of _basic_slice_meta utility function to correctly handle
boolean scalars (surprisingly, `insinstance(True, int)` evaluates to `True`).
0d arrays are handled by Python scalars.

Introduced _is_integral and _is_boolean utilty functions and used them in
`_basic_slice_meta` utility.

Author: oleksandr-pavlyk

dpctl/tensor/_slicing.pxi

@@ -1,6 +1,6 @@
 #                       Data Parallel Control (dpctl)
 #
-#  Copyright 2020-2022 Intel Corporation
+#  Copyright 2020-2023 Intel Corporation
 #
 #  Licensed under the Apache License, Version 2.0 (the "License");
 #  you may not use this file except in compliance with the License.
@@ -15,6 +15,11 @@
 #  limitations under the License.
 
 import numbers
+from cpython.buffer cimport PyObject_CheckBuffer
+
+
+cdef bint _is_buffer(object o):
+    return PyObject_CheckBuffer(o)
 
 
 cdef Py_ssize_t _slice_len(
@@ -36,14 +41,23 @@ cdef Py_ssize_t _slice_len(
 
 cdef bint _is_integral(object x) except *:
     """Gives True if x is an integral slice spec"""
-    if isinstance(x, (int, numbers.Integral)):
-        return True
     if isinstance(x, usm_ndarray):
         if x.ndim > 0:
             return False
         if x.dtype.kind not in "ui":
             return False
         return True
+    if isinstance(x, bool):
+        return False
+    if isinstance(x, int):
+        return True
+    if _is_buffer(x):
+        mbuf = memoryview(x)
+        if mbuf.ndim == 0:
+           f = mbuf.format
+           return f in "bBhHiIlLqQ"
+        else:
+           return False
     if callable(getattr(x, "__index__", None)):
         try:
             x.__index__()
@@ -53,6 +67,34 @@ cdef bint _is_integral(object x) except *:
     return False
 
 
+cdef bint _is_boolean(object x) except *:
+    """Gives True if x is an integral slice spec"""
+    if isinstance(x, usm_ndarray):
+        if x.ndim > 0:
+            return False
+        if x.dtype.kind not in "b":
+            return False
+        return True
+    if isinstance(x, bool):
+        return True
+    if isinstance(x, int):
+        return False
+    if _is_buffer(x):
+        mbuf = memoryview(x)
+        if mbuf.ndim == 0:
+           f = mbuf.format
+           return f in "?"
+        else:
+           return False
+    if callable(getattr(x, "__bool__", None)):
+        try:
+            x.__bool__()
+        except (TypeError, ValueError):
+            return False
+        return True
+    return False
+
+
 def _basic_slice_meta(ind, shape : tuple, strides : tuple, offset : int):
     """
     Give basic slicing index `ind` and array layout information produce
@@ -82,6 +124,11 @@ def _basic_slice_meta(ind, shape : tuple, strides : tuple, offset : int):
             _no_advanced_ind,
             _no_advanced_pos
         )
+    elif _is_boolean(ind):
+        if ind:
+            return ((1,) + shape, (0,) + strides, offset, _no_advanced_ind, _no_advanced_pos)
+        else:
+            return ((0,) + shape, (0,) + strides, offset, _no_advanced_ind, _no_advanced_pos)
     elif _is_integral(ind):
         ind = ind.__index__()
         if 0 <= ind < shape[0]:
@@ -117,6 +164,10 @@ def _basic_slice_meta(ind, shape : tuple, strides : tuple, offset : int):
                 axes_referenced += 1
                 if array_streak_started:
                     array_streak_interrupted = True
+            elif _is_boolean(i):
+                newaxis_count += 1
+                if array_streak_started:
+                    array_streak_interrupted = True
             elif _is_integral(i):
                 explicit_index += 1
                 axes_referenced += 1
@@ -133,9 +184,9 @@ def _basic_slice_meta(ind, shape : tuple, strides : tuple, offset : int):
                         "separated by basic slicing specs."
                     )
                 dt_k = i.dtype.kind
-                if dt_k == "b":
+                if dt_k == "b" and i.ndim > 0:
                     axes_referenced += i.ndim
-                elif dt_k in "ui":
+                elif dt_k in "ui" and i.ndim > 0:
                     axes_referenced += 1
                 else:
                     raise IndexError(
@@ -186,6 +237,9 @@ def _basic_slice_meta(ind, shape : tuple, strides : tuple, offset : int):
                 if sh_i == 0:
                     is_empty = True
                 k = k_new
+            elif _is_boolean(ind_i):
+                new_shape.append(1 if ind_i else 0)
+                new_strides.append(0)
             elif _is_integral(ind_i):
                 ind_i = ind_i.__index__()
                 if 0 <= ind_i < shape[k]: