Crosscompiling python extensions using host python

[Neumann-A]

• wait for [python3] Add import test for extensions microsoft/vcpkg#39449 to be merged
• do what crossenv does but with vcpkg_get_vcpkg_installed_python manually (I don't think crossenv is required)
• copy over CURRENT_INSTALLED_DIR libs instead of host python
• (!windows) Copy over CURRENT_INSTALLED_DIR _sysconfig_data_<something> (might have to mimic the host one?)
• (windows) might need to adress the TODO in vcpkg_get_vcpkg_installed_python about the suffix
• Might need to create a real venv by copying Libs and site-packages more isolated to not accidentally cross host and target somehow.