Mvc.Api.Analyzers should treat `IResult` types correctly

A support for `IResults` types in MVC Action controller is going to be added by #40710, however Mvc.Api.Analyzers still treat IResult returned instances as user defined `Model`, that basically means an OkResult (HTTP Status Code: 200) and might suggest the adding of incorrect Produces* attributes or incorrect warnings.

Relevant code: https://github.com/dotnet/aspnetcore/blob/main/src/Mvc/Mvc.Api.Analyzers/src/ActualApiResponseMetadataFactory.cs

_Originally posted by @pranavkm in https://github.com/dotnet/aspnetcore/issues/40710#issuecomment-1068686855_