Handle `AsParameters`-enabled types with indexers in request delegate creation

[captainsafia]

Follow-up to #47914 (comment).

The implementation for the AsParameters feature in both RDF and RDG doesn't currently handle types that contain indexers:

public class ClassWithIndexer
{
    private int[] arr = new int[100];

    public int this[int i]
    {
        get { return arr[i]; }
        set { arr[i] = value; }
    }
}

We'll want to explore either:

• Adding support for this feature
• Explicitly disabling support for types that contain indexers with RDF

If we do consider adding support, we may want to tie this with the existing array binding features in RDF.

[amcasey]

Don't forget that indexers can be named, either natively in a language like VB or via an attribute.

[captainsafia]

Don't forget that indexers can be named, either natively in a language like VB or via an attribute.

Good note! VB is out-of-scope but we should keep the IndexerNameAttribute in mind for this implementation.

[amcasey]

Oh cool, I forgot we didn't have to think about types from metadata. That sure makes things easier. 😄

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.