Fix some build warnings

This PR fixes some build warnings I stumbled upon while testing the compatibility of Gamera with the upcoming Python 3.12 release.

Included fixes:

`pkg_resources.parse_version` is deprecated

../../../../../opt/hostedtoolcache/Python/3.12.0-alpha.7/x64/lib/python3.12/site-packages/pkg_resources/__init__.py:121
  /opt/hostedtoolcache/Python/3.12.0-alpha.7/x64/lib/python3.12/site-packages/pkg_resources/__init__.py:121: DeprecationWarning: pkg_resources is deprecated as an API
    warnings.warn("pkg_resources is deprecated as an API", DeprecationWarning)

The pkg_resources.parse_version calls have been removed completely, as docutils==0.4 and pygments==0.6 have been released in 2006. Additionally, support for lexing using SilverCity has been dropped as well, as the package had its last release in 2005: https://pypi.org/project/SilverCity/

Invalid escape sequences for regex expressions

  /home/runner/work/gamera-4/gamera-4/gamera/pyplate.py:59: SyntaxWarning: invalid escape sequence '\['
    re_directive = re.compile("\[\[(.*?)\]\]")
  /home/runner/work/gamera-4/gamera-4/gamera/pyplate.py:63: SyntaxWarning: invalid escape sequence '\('
    re_def = re.compile("def (.*?)\((.*)\)")
  /home/runner/work/gamera-4/gamera-4/gamera/pyplate.py:64: SyntaxWarning: invalid escape sequence '\('
    re_call = re.compile("call (.*?)\((.*)\)")

There were multiple places where I got syntax warnings due to invalid escape sequences. This has been fixed by converting this strings to raw ones.

Comparison of integer expressions of different signedness

  src/knncore/knncoremodule.cpp: In function ‘PyObject* knn_set_selections(PyObject*, PyObject*)’:
  src/knncore/knncoremodule.cpp:1387:24: warning: comparison of integer expressions of different signedness: ‘Py_ssize_t’ {aka ‘long int’} and ‘size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
   1387 |         if (buffer.len != o->num_features * sizeof(int)) {
        |             ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  src/knncore/knncoremodule.cpp: In function ‘PyObject* knn_set_weights(PyObject*, PyObject*)’:
  src/knncore/knncoremodule.cpp:1423:24: warning: comparison of integer expressions of different signedness: ‘Py_ssize_t’ {aka ‘long int’} and ‘size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
   1423 |         if (buffer.len != o->num_features * sizeof(double)) {
        |             ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There have been some length comparisons with non-matching data types, which has been corrected by applying the corresponding cast on the left-hand sides.

uint32 deprecation warnings from libtiff

  /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp: In function ‘Gamera::ImageInfo* Gamera::tiff_info(const char*)’:
  /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp:71:12: warning: ‘uint32’ is deprecated [-Wdeprecated-declarations]
     71 |     uint32 size;
        |            ^~~~
  In file included from /usr/include/x86_64-linux-gnu/tiffio.h:31,
                   from /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp:28,
                   from gamera/plugins/_tiff_support.cpp:7:
  /usr/include/x86_64-linux-gnu/tiff.h:84:38: note: declared here
     84 | typedef TIFF_MSC_DEPRECATED uint32_t uint32 TIFF_GCC_DEPRECATED;
        |                                      ^~~~~~
  In file included from gamera/plugins/_tiff_support.cpp:7:
  /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp: In member function ‘void Gamera::{anonymous}::tiff_saver<short unsigned int>::operator()(const T&, TIFF*)’:
  /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp:259:15: warning: ‘uint32’ is deprecated [-Wdeprecated-declarations]
    259 |       uint32* data = (uint32 *)buf;
        |               ^~~~
  In file included from /usr/include/x86_64-linux-gnu/tiffio.h:31,
                   from /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp:28,
                   from gamera/plugins/_tiff_support.cpp:7:
  /usr/include/x86_64-linux-gnu/tiff.h:84:38: note: declared here
     84 | typedef TIFF_MSC_DEPRECATED uint32_t uint32 TIFF_GCC_DEPRECATED;
        |                                      ^~~~~~
  In file included from gamera/plugins/_tiff_support.cpp:7:
  /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp:259:30: warning: ‘uint32’ is deprecated [-Wdeprecated-declarations]
    259 |       uint32* data = (uint32 *)buf;
        |                              ^
  In file included from /usr/include/x86_64-linux-gnu/tiffio.h:31,
                   from /home/runner/work/gamera-4/gamera-4/gamera/include/gamera/plugins/tiff_support.hpp:28,
                   from gamera/plugins/_tiff_support.cpp:7:
  /usr/include/x86_64-linux-gnu/tiff.h:84:38: note: declared here
     84 | typedef TIFF_MSC_DEPRECATED uint32_t uint32 TIFF_GCC_DEPRECATED;
        |                                      ^~~~~~

The corresponding sections have been replaced to use the _t type versions (standardized C99 types) as proposed in http://libtiff.maptools.org/v4.3.0.html

Drop old multiprocessing.pool workaround

The multiprocessing.pool workaround for the build (instead of concurrent.futures) has been removed as it has been documented to be for some older Python 2.x releases only. As we are not supporting Python 2 any more, this is not required here.

`setup.py install` deprecation warning

 /opt/hostedtoolcache/Python/3.12.0-alpha.7/x64/lib/python3.12/site-packages/setuptools/command/install.py:34: SetuptoolsDeprecationWarning: setup.py install is deprecated. Use build and pip and other standards-based tools.
    warnings.warn(

Strangely enough, we have already been using pip install . beforehand. According to https://stackoverflow.com/questions/70970858/what-is-the-best-replacement-for-python-setup-py-install-when-cython-needs-to-be, a pyproject.toml file avoids this and thus has been implemented.

hsnr-gamera / gamera-4