Support `vtkBitArray` creation in `vtk.util.numpy_support.numpy_to_vtk`

Description

When attempting to create a vtkBitArray by specifying array_type=vtk.VTK_BIT, the resulting array is invalid.

Specifically, boolean values in the original NumPy array are not accurately preserved in the VTK array:

import numpy as np
import vtk

narray = np.array([True, False, True])
vtk_array = vtk.util.numpy_support.numpy_to_vtk(narray, array_type=vtk.VTK_BIT)

assert vtk_array.GetValue(0) == 1, "Expected value at index 0 to be 1"
assert vtk_array.GetValue(1) == 0, "Expected value at index 1 to be 0"
assert vtk_array.GetValue(2) == 1, "Expected value at index 2 to be 1"

Traceback (most recent call last):
  File "<string>", line 7, in <module>
AssertionError: Expected value at index 0 to be 1

The above assertions currently fail because vtk_array does not store the correct bit values.

Suggested Approach

A possible solution is to enhance numpy_to_vtk to properly handle boolean arrays by packing bits. The snippet below demonstrates a concept for handling VTK_BIT:

import numpy as np
import vtk

def _numpy_to_vtk(narray, deep=False, array_type=None):
    if array_type == vtk.VTK_BIT:
        packed_bits = np.packbits(narray)
        result_array = vtk.util.numpy_support.create_vtk_array(array_type)
        result_array.SetNumberOfComponents(1)
        shape = narray.shape
        result_array.SetNumberOfTuples(shape[0])
        result_array.SetVoidArray(packed_bits, shape[0], 1)
        # Since packed_bits is a standalone object with no references from the caller.
        # As such, it will drop out of this scope and cause memory issues if we
        # do not deep copy its data.
        copy = result_array.NewInstance()
        copy.DeepCopy(result_array)
        result_array = copy
        return result_array
    
    return numpy_support.numpy_to_vtk(narray, deep=deep, array_type=array_type)

# Test the modified function
vtk_array_2 = _numpy_to_vtk(narray, array_type=vtk.VTK_BIT)
assert vtk_array_2.GetValue(0) == 1, "Expected value at index 0 to be 1"
assert vtk_array_2.GetValue(1) == 0, "Expected value at index 1 to be 0"
assert vtk_array_2.GetValue(2) == 1, "Expected value at index 2 to be 1"

Additional Context

• By using np.packbits, the boolean array is converted into a bit-packed representation suitable for vtkBitArray.
• A deep copy is required to avoid memory reference issues once packed_bits goes out of scope.
• Integrating similar logic into numpy_to_vtk would allow easy creation of vtkBitArray from boolean NumPy arrays.