Add a new docs section "Building a package"

From https://github.com/mesonbuild/meson-python/pull/634#issuecomment-2119236087:

@dnicolodi suggested:
_I wonder whether it is time to have a Building a package top sections in the documentation with the details about build isolation, venv and some hints about cibuildwheel and co for building redistributable wheels._

@rgommers replied:

_Yes, I agree. This is the cause of a lot of the questions/issues we are receiving. I also just searched for `auditwheel` and it's not in our docs (except in the non-public `explanations/design-old.rst`)._

_I won't be able to work on that in the next few days though, since it'll take a few hours at least to do it right. Should we open a new issue for that first, and scope it? I think I'd prefer to address your one comment here, and then have a new PR for the new docs page, containing:_
- _The content added here_
- _Content from `design-old.rst`_
- _Mentioning all the relevant tools._
- _I'd like to refer to https://pypackaging-native.github.io/meta-topics/build_steps_conceptual/#building-and-installing-or-uploading-artifacts, which explains a lot of things that are relevant here._

We do indeed get lots of variations of the same questions that are conceptual issues with how Python packaging works and how `meson-python` fits in. I'm under no illusion that all users are going to understand build isolation and the difference between local and redistributable wheels, but it'd be nice if we could reply with a one-liner linking to the docs.

Inizia esaminando la discussione nella pull request 634 e la spiegazione non pubblica esistente in design-old.rst. Usa come contesto la pagina collegata sui passaggi di build del packaging, quindi definisci una nuova sezione della documentazione che tratti l’isolamento delle build, gli ambienti virtuali, le wheel locali rispetto a quelle redistribuibili, cibuildwheel, auditwheel e altri strumenti pertinenti; il lavoro è completato quando questi argomenti sono spiegati e collegati dalla documentazione.

Scritto dal modello di indicizzazione a partire dal testo della issue.