[docs] AppleVZ docs

[sharder996]

This PR adds references in the docs to the new AppleVZ backend driver.

---

MULTI-2529

[geoffreynyaga]

Just a small fix.
We should use US english for consistency. I'd recommend we swap virtualisation with virtualization. This also helps with consistency even when we reference AppleVZ.

Note: US english is now recommended internally https://docs.ubuntu.com/styleguide/en/#spelling and the word 'virtualization' is specifically listed under the "Other common terms" section. The functionality is already implemented in the Multipass repo, but we have not enabled the check on CI (it requires effort to update all pages). Hint: If you run make run locally, you should see a docs/.sphinx/styles/Canonical/000-US-spellcheck.yml file.

[sharder996]

I used virtualization explicitly because its part of the name of the framework, but if you want I can find/replace all instances of virtualisation with the former.

[geoffreynyaga]

Minor request. Since we use both the full name and the abbreviation interchangeably throughout the docs, I'd suggest introducing both together at first mention so readers always have the reference:

+ the Apple Virtualization framework (AppleVZ), ...

Quick question: I know that Apple uses VZ as class prefix throughout its codebase. Are apple-vz/AppleVZ terms that Apple uses officially, or are they Multipass-specific shorthands derived from that prefix? Knowing this will help us write a more accurate explanation in the docs down the line.

[sharder996]

I have found no references to any other AppleVZ mutations in the Apple docs. Its always referred to by its full moniker.

[ricab]

Will the setting value be named as applevz? If so, better tie the two together somewhere in the docs (not sure where)

[sharder996]

It is mentioned in

multipass/docs/how-to-guides/customise-multipass/set-up-the-driver.md

Lines 35 to 48 in ba40c5e

	## Install an alternative driver
	`````{tab-set}
	````{tab-item} macOS
	:sync: macOS
	An alternative option is to use the Apple Virtualization framework.
	To switch the Multipass driver to AppleVZ, run this command:
	```{code-block} text
	sudo multipass set local.driver=applevz
	```