Implement IOperation support for tuple literals

[VSadov]

Design and implement IOperation support for tuple literals.

Current implementation intentionally implements this as OperationKind.None

The right alternative seems to be introducing a specific operation kind and make visitor visit all the arguments of the literal.

Alternatively we may make tuple literals look like ObjectCreation (which it is indirectly), but it does not feel right conceptually.

[mavasani]

Possible API shape:

    public interface ITupleExpression : IOperation
    {
        /// <summary>
        /// Arguments for tuple expression.
        /// </summary>
        ImmutableArray<IOperation> Arguments { get; }
    }

Points to discuss:

1. Should the API expose the optional tuple argument names?
2. Bound tree has a separate BoundConvertedTupleLiteral node, which is identical to BoundTupleLiteral, except it represents a tuple literal with source type and destianation. I don't believe we should have this in the IOperation API - instead we should just wrap an ITupleExpression with an IConversion for a BoundConvertedTupleLiteral.

[mavasani]

Adding some design issues raised by Aleksey in the PR to implement this:

1. Need to expose declaration expression nodes as a special Operation type: Add IOperation support for tuple expressions #19636 (comment)
2. Bunch of unexpected conversions: Add IOperation support for tuple expressions #19636 (comment). Is this a compiler issue or Operation factory needs to filter out unwanted conversion nodes? @AlekseyTs suggested we need to have a design discussion around tuple conversions: Add IOperation support for tuple expressions #19636 (comment)

[CyrusNajmabadi]

Design Team Discussion

Keep tuple tests with semantic model tests around tuples.
Try to keep IOperation for tuples in sync with semanticmodel.GetTypeInfo. That way we don't have two separate APIs that people can use that have inconsistent results.

[mavasani]

Fixed with #20749