AccessorSlot and LambdaAccessorSlot should populate value in Property Descriptor

[nabacg]

Follow up on #1577 , AccessorSlot and LambdaAccessorSlot should add value attribute to their Property Descriptor when getter / setter are not set.

Use cases to where it matters:
When somePDInstance.value will return undefined in both cases, but these will display different behavior:

• somePDInstance.hasOwnProperty/Object.hasOwn: false vs. true
• Object.getOwnPropertyDescriptor: undefined vs. Object
• Object.getOwnPropertyDescriptors/Object.keys/Object.entries: missing entry for value property PD vs including a PD for the value property
• forOf/forIn loops won't include the missing value property

from, there is a good discussion in PR review with a lot more details.

How it works in Chrome / Node

> const o = {};
undefined

>Object.defineProperty(o, "b", {
		enumerable: true,
		configurable: true
});
{b: undefined}


> Object.getOwnPropertyDescriptor(o, "b")
{value: undefined, writable: false, enumerable: true, configurable: true}

[p-bakker]

@nabacg think you might create a PR for this one, or even a larger PR fixing some of the other PropertyDescriptor related cases as well?

[tonygermano]

I think by definition an Accessor Property,

1. must have a Get or Set slot where at least one of them holds a reference to a Callable. The other can also be a Callable or undefined.
2. must not have a value slot

In your example, that would create a Data Property, not an Accessor Property, because it has neither a get nor set method defined.

[tonygermano]

For example, also in Chrome (note that when I provide a get method, the descriptor has a property set with an undefined value, but no properties called value or writable because those belong to Data Properties):

>  const o = {}
<- undefined

>  Object.defineProperty(o, "b", {
    enumerable: true,
    configurable: true,
    get() { return "c" }
})
    
<- {}
>  Object.getOwnPropertyDescriptor(o, "b")
<- {set: undefined, enumerable: true, configurable: true, get: ƒ}