Currently it is unsupported to:
1. Convert a `MlirAttribute` with type `i1` to a numpy array
2. Convert a boolean numpy array to a `MlirAttribute`
Currently the entire Python application violently crashes with a quite
poor error message https://github.com/pybind/pybind11/issues/3336
The complication handling these conversions, is that `MlirAttribute`
represent booleans as a bit-packed `i1` type, whereas numpy represents
booleans as a byte array with 8 bit used per boolean.
This PR proposes the following approach:
1. When converting a `i1` typed `MlirAttribute` to a numpy array, we can
not directly use the underlying raw data backing the `MlirAttribute` as
a buffer to Python, as done for other types. Instead, a copy of the data
is generated using numpy's unpackbits function, and the result is send
back to Python.
2. When constructing a `MlirAttribute` from a numpy array, first the
python data is read as a `uint8_t` to get it converted to the endianess
used internally in mlir. Then the booleans are bitpacked using numpy's
bitpack function, and the bitpacked array is saved as the
`MlirAttribute` representation.
Please note that I am not sure if this approach is the desired solution.
I'd appreciate any feedback.
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