Test against PHP 8.2, and maybe 8.3

[GaryJones]

What problem would the enhancement address for VIP?

PHP 8.2 is released, and we should check how VIPCS works with it, even though WordPress itself doesn't yet support PHP 8.2.

Describe the solution you'd like

Add 8.2 to the test.yml matrix. We'll also want to use dev-develop version of WPCS as well.

Also, add 8.3 as an include, but allow it to be experimental.

[jrfnl]

💯 Was thinking the same yesterday when reviewing #742, but didn't want to pollute the issue with unrelated remarks.

[jrfnl]

Notes about PHPCS vs 8.2:

• PHP 8.2 doesn't introduce a huge amount of syntax changes, so is nowhere near as problematic as some of the previous PHP releases.
• PR to support readonly classes is open and expected to be merged in PHPCS 3.8.0.
• Follow up PR to add support for readonly classes to various sniffs has been prepared.
• Big "still to do": add Tokenizer support for DNF (mixing intersection and union types and using parentheses in types - will probably mean that a new T_OPEN_TYPE_PARENS token will need to be introduced (and similar for close parens).