nimi-python functions that take paths do not accept `pathlib.Path` objects

[bkeryan]

Description of issue

nimi-python has a number of API functions that take paths, such as import_attribute_configuration_file and nidigital's load_pin_map, load_specifications_levels_and_timing, and load_pattern.

Most of these only accept str. Some also accept Iterable[str].

pathlib has been part of the Python standard library since Python 3.4, so it would be nice if nimi-python supported it.

System report

python -c "import nidigital; nidigital.print_diagnostic_information()" output

OS:
    Name:      Windows
    Version:   10.0.19045
    Bits:      64
Driver:
    Name:      NI-Digital Pattern Driver
    Version:   Unknown
Module:
    Name:      nidigital
    Version:   1.4.4
Python:
    Version:   3.9.13 (tags/v3.9.13:6de2ca5, May 17 2022, 16:36:42) [MSC v.1929 64 bit (AMD64)]
    Bits:      64
    Is_Venv:   True
    Installed Packages:
        click==8.1.3
        colorama==0.4.6
        grpcio==1.53.0
        hightime==0.2.1
        mypy==1.2.0
        mypy-extensions==1.0.0
        ni-measurementlink-service==1.0.1
        nidigital==1.4.4
        nitclk==1.4.4
        pip==23.0.1
        protobuf==4.22.3
        pywin32==303
        setuptools==67.6.1
        tomli==2.0.1
        typing-extensions==4.5.0
        wheel==0.40.0

Steps to reproduce issue

1. Run this on a system with an NI Digital Pattern instrument installed, using files from the LabVIEW SPI example:

import nidigital
import pathlib

session = nidigital.Session("DigitalPattern1")
session.load_pin_map(pathlib.Path("PinMap.pinmap"))
session.load_specifications_levels_and_timing(pathlib.Path("Specifications.specs"), pathlib.Path("PinLevels.digileve
ls"), pathlib.Path("Timing.digitiming"))

load_pin_map error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\dev\measurementlink-python\examples\nidigital_spi\.venv\lib\site-packages\nidigital\session.py", line 41, in aux
    return f(*xs, **kws)
  File "D:\dev\measurementlink-python\examples\nidigital_spi\.venv\lib\site-packages\nidigital\session.py", line 3683, in load_pin_map
    self._interpreter.load_pin_map(file_path)
  File "D:\dev\measurementlink-python\examples\nidigital_spi\.venv\lib\site-packages\nidigital\_library_interpreter.py", line 729, in load_pin_map
    file_path_ctype = ctypes.create_string_buffer(file_path.encode(self._encoding))  # case C020
AttributeError: 'WindowsPath' object has no attribute 'encode'

load_specifications_levels_and_timing error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\dev\measurementlink-python\examples\nidigital_spi\.venv\lib\site-packages\nidigital\session.py", line 41, in aux
    return f(*xs, **kws)
  File "D:\dev\measurementlink-python\examples\nidigital_spi\.venv\lib\site-packages\nidigital\session.py", line 3451, in load_specifications_levels_and_timing
    self._call_method_with_iterable(self._load_specifications, specifications_file_paths)
  File "D:\dev\measurementlink-python\examples\nidigital_spi\.venv\lib\site-packages\nidigital\session.py", line 3460, in _call_method_with_iterable
    for f in files:
TypeError: 'WindowsPath' object is not iterable
    ```

### Workaround

Call `str(...)` on `Path` objects before passing them to nimi-python.