431 on windows cmake variable set khiops drivers path is not substituted correctly in khiops envcmd

[popescu-v]

Fix KHIOPS_DRIVERS_PATH setting in the Windows khiops_env template script by the packaging/install.cmake CMake script for Conda on Windows. Fix the NSIS Windows native packaging script so that it uses the instantiated khiops_env template instead of the template script itself.

[popescu-v]

Cela me semble correct.

Je pense que l'on pourrait profiter de cette PR pour traiter les points de détail suivants:

* dans les khiops_env.*.in (Windows et Linux)

  * remplacer les commentaires
    `KHIOPS_PATH: path of Khiops executable, to add in path`
    `KHIOPS_COCLUSTERING_PATH: path of Khiops coclustering executable, to add in path`
    par
    `KHIOPS_PATH: full path of Khiops executable`
    `KHIOPS_COCLUSTERING_PATH: full path of Khiops coclustering executable`

* dans WHATSNEW.txt

  * ajouter un ligne blanche avant la section "Version 10.2.2"

Sinon, un détail: 4 points de commits me semblent un peu beaucoup. On pourrait se contenter de deux commits:

* un de type "Fixed a bug in the driver path setting in khipps_env"

* l'autre restant "Update Khiops version to 10.2.3-rc.2" (avec la ligne blanche du WHATSNEW.txt)

Requested changes done. Kept 4 commits, but this includes the supplemental changes related to the khiops_env help and WHATSNEW.txt updates.