[10.x] Allow object caching to be disabled for custom class casters

[calebdw]

Hello!

This is in a similar vein as #40519, but for custom class casters. I need to disable object caching but there's currently no way to do this with custom casters. This PR allows a boolean withoutObjectCaching property to be defined on the class casters which HasAttributes then checks for before caching.

Thanks!

[JamShady]

I realise I'm a little late to the discussion on this, but was/is there a reason this property has to be named 'withoutObjectCaching' (i.e. negative) that defaults to false, rather than just something like 'cacheObject' which defaults to true?

In my mind, I've got to do unnecessary mental gymnastics in thinking "I want object caching, therefore my desired value is true, but the variable is in the negative, so I have to flip my desired value around and set to false", as opposed to the other way which would be "I don't want object caching, so I just set the value to false" which is far less neural load and less likely to be set incorrectly, resulting in less potential developer frustration when it turns out they accidentally set the wrong value due to this confusion.

I hope that makes sense.

Sorry to tag you @taylorotwell I wasn't sure if you'd get notified otherwise. I'm happy to put in a PR for this if you deem it a good idea?

[calebdw]

@JamShady,

Yes there were reasons:

1. It follows the same public api as ->withoutObjectCaching() for mutators
2. The default behaviour is object caching and can't force everyone to have to add the property to their class in order for default behaviour to continue working (breaking change)
3. Not a fan of a missing property defaulting to true, a missing property should be considered "falsey" in my opinion
4. There's no reason to ever specify $withoutObjectCaching = false if you want the default behaviour, you should only add the property to the class if you want to disable caching in which case $withoutObjectCaching = true reads better (the boolean is really just for completeness, code could have just checked for property existence).

It's pretty clear to me what the property does and doesn't require a lot of "mental gymnastics" to understand that the value should be set to true if you want to disable object caching...