Use non-BOM encodings (#2370)

* Use non-BOM encodings

The documentation of the used `PyUnicode_DecodeUTF16` states that not passing `*byteorder` or passing a 0 results in the first two bytes, if
they are the BOM (U+FEFF, zero-width no-break space), to be interpreted and skipped, which is incorrect when we convert a known "non BOM" string, which all strings from C# are.