doc:it_IT: add some process/* translations

This patch does not translate entirely the subfolder "process/"
but only part of it (to begin with).

In order to avoid broken links, I included empty documents
for those which are not yet translated.

In order to be able to refer to all documents in "process/",
I added a sphinx label to those which had not one.

Translated documents:
- howto
- 1.Intro
- clang-format
- coding-style
- kernel-driver-statement
- magic-number
- volatile-considered-harmful
- development-process

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Alessia Mantegazza <amantegazza@vaga.pv.it>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>