Allow using 'using' in foreach for the enumerable.

[Raphtaliyah]

If an enumerable type implements IDisposable (or the dispose pattern for ref structs) and an instance would only be created to be enumerated, currently there is no way to use it in a foreach loop without using a local variable.
This proposal is to allow using using inside the "header" of the foreach loop like this:

foreach (var entity in using View.Create<Test>(game))
{
    // code
}

The example is from an ECS where the created View holds unmanaged memory and must be disposed, finalizers can't be used because the View is a ref struct. The current workaround is to have a local variable:

using var view = View.Create<Test>(game);
foreach (var entity in view)
{
    // code
}

The local variable is completely unnecessary unless it's enumerated multiple times, which is rarely the case and requires longer names if multiple Views are created in the same scope. Allowing using inside the foreach loop would help clean up this and code similar to this.

The lifetime of the enumerable would either match the lifetime of the View in the local variable example or would be disposed at the end of the foreach loop.