Generic CreateMarshaler

[j0shuams]

This PR adds a new public API to MarshalInspectable, which allows calls to CreateMarshaler to pass in a VTable as generic param and an IID as a function param. This reduces .As() call and prevents unnecessary allocations.

In the table below, "Unwrap" refers to the case where CreateMarshaler returns early, and "CreateCCW" is the case where CreateMarshaler calls the CreateCCW function. Time is measured in microseconds (us) and memory is measured in bytes (B).

Net5.0

Codepath	Master - time	Topic - time	Master - memory	Topic - memory
Unwrap	5.243 us	4.947 us	464 B	344 B
CreateCCW	10.784 us	8.52 us	768 B	648 B

NetStandard2.0

Codepath	Master - time	Topic - time	Master - memory	Topic - memory
Unwrap	8.997 us	8.288 us	1560 B	1440 B
CreateCCW	69.445 us	67.744 us	4400 B	4241 B

While saving only a microsecond or two, we consistently use at least 120 B less of memory everytime we call CreateMarshaler.

Will provide a diff of generated code

Below is an example of a common pattern in projected code for structs used with marshaling, we provide a new (generic) function that handles the implementation that does not need the same subsequent method calls.

namespace ABI.Windows.System.Profile
{
    [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
    public struct AnalyticsVersionInfo
    {
        public static IObjectReference CreateMarshaler(global::Windows.System.Profile.AnalyticsVersionInfo obj) => 
          obj is null ? 
            null : 
            // new 
             MarshalInspectable<global::Windows.System.Profile.AnalyticsVersionInfo>.CreateMarshaler<IUnknownVftbl>(obj, GuidGenerator.GetIID(typeof(global::Windows.System.Profile.IAnalyticsVersionInfo).GetHelperType())
            /* old 
             MarshalInspectable<global::Windows.System.Profile.AnalyticsVersionInfo>.CreateMarshaler(obj).As<IUnknownVftbl>(GuidGenerator.GetIID(typeof(global::Windows.System.Profile.IAnalyticsVersionInfo).GetHelperType()) */
           );
    }
}