Fix the error caused by non-decodable bytes when retrieving the non-empty domain for TILEDB_ASCII dimensions

[kounelisagis]

As discovered in TileDB-ML, calling the Array::_non_empty_domain pybind11 function on a TILEDB_ASCII dimension containing non-decodable bytes (in terms of UTF-8) resulted in errors such as:
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x81 in position 0: invalid start byte.
The pybind11::make_tuple function assumed that the input would always be a printable string, requiring special handling for this case.
This PR addresses the issue and also ensures that an exception is thrown for dimensions of unicode string type, as this is not supported until TileDB 2.27.0.

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[sc-63472]

[ihnorton]

LGTM after double-checking the return type matches 0.32

[ktsitsi]

Confirming changes fix the issue in TileDB-ML.

[kounelisagis]

LGTM after double-checking the return type matches 0.32

Both the structure of the returned value from Array::_non_empty_domain (a tuple of tuples - one for each dimension) and the type of each internal tuple (bytes, in this case) remain the same.