C#: Untyped to typed ArgumentNullException

[Repiteo]

Originally part of #82983, before one of the discussions prompted me to check if adding ArgumentNullException to the untyped→typed constructors would break compatability. As it turns out, it would not, because they always expect the underlying collection to be valid. However, this does mean that it wasn't throwing an exception earlier, only when an actual function is called, so the exception in the constructor is warranted

In addition, this adds missing exception/returns documentation for the two files. It was already warranted for the constructors having a new exception, but this ensures similar relevant functions have appropriate documentation if it was similarly missing

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Test case::

var array = (Godot.Collections.Array)null;
var intArray = new Godot.Collections.Array<int>(array);
intArray.Add(123);

Old behavior log, caught on line 3:

Array.cs:1514 @ Boolean Godot.Collections.Array`1.get_IsReadOnly(): System.NullReferenceException: Object reference not set to an instance of an object.

New behavior log, caught on line 2:

Array.cs:1129 @ Godot.Collections.Array`1..ctor(Godot.Collections.Array): System.ArgumentNullException: Value cannot be null. (Parameter 'array')

[raulsntos]

Looks good to me, since it was already resulting in exceptions I think it's fine to move the exception to the constructor.

[akien-mga]

Thanks!