int_conv: Add more integer type binding and add a unit test

changelog: Add changelog entry

int_conv: Manage int8_t and long on Windows

int_conv: Try to use stdint type to manage long hack on windows

int_conv: Fix Windows build

int_conv: Try to fix Mac build and don't compile twice 64 bits integer on Mac and Windows

int_conv: Don't use np.dtypes (introduced in numpy 1.25)

int_conv: Test long and int difference in unit test

[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

int_conv: Expose long in MacOS

int_conv: Don't use deprecated type np.intc

int_conv: Fix Mac build

int_conv: Remove int128 (doesn't exists)

int_conv: Disable long long test on Mac because the type is not reachable

int_conv: Begin to work on promotion

int_conv: Add unsigned promotion

int_conv: Manage complex promotion

int_conv: Split matrix binding to avoid memory issue while building

int_conv: Split decomposition binding to avoid memory issue while building

int_conv: Use clongdouble instead of complex256

int_conv: Avoid out of heap space error on Windows

int_conv: Fix test for Mac

int_conv: Try to manage longlong on Mac and int on Windows, also reduce compile time

int_conv: Manage Windows and Mac int and long long when casting

int_conv: Allow scalar to complex conversion

int_conv: Manage casting from numpy to eigen with tensor

int_conv: Add changelog entries

int_conv: Remove conversion from Eigen to Numpy

int_conv: Add reference to this PR

int_conv: Activate SciPy tests by default

which might not be "include"

This feature is only available on Mac OS X, with Eigen >= 3.4.90

ref. https://github.com/jrl-umi3218/jrl-cmakemodules/issues/338
and fix deprecation warning about CMake 3.5 from CMake 3.27

* optional: expose to-value converter for boost::none_t (and std::nullopt_t if possible)

+ add src/optional.cpp to expose none types
+ this allows to have None as a default arg value for functions (also, shows up in stubs)
+ also allows to have none_t return/argument type

* Run pre-commit

+ default is boost::optional<T>
+ add test for boost::optional

* add test_std_vector.py
* fix copyable.hpp's include guards & namespace
* same for pickle-vector
* expose std::vector for VectorXd, MatrixXd, VectorXi, MatrixXi