Document use of OWIN bridge to host ASP.NET Web API in ASP.NET Core

This doc does a reasonable job of describing how to migrate an ASP.NET Web API controller to ASP.NET Core. However, often users have lots of web API controllers that they can't afford to migrate all at once. Instead, they can migrate their app to ASP.NET Core by hosting ASP.NET Web API in ASP.NET Core through the OWIN bridge and then migrate individual web API controllers to ASP.NET Core over time. We should update this doc to show how to host ASP.NET Web API in ASP.NET Core as a migration strategy. Here's a sample that shows how to do this: https://github.com/danroth27/AspNetWebApiCore

We should document how to host OWIN based frameworks in ASP.NET Core (https://github.com/dotnet/AspNetCore.Docs/issues/25663) and document specifically how to host ASP.NET Web API in ASP.NET Core in this migration topic.

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#### Document Details

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* ID: 6f83a3b4-28f6-5f0f-a8bf-aef76f05fe42
* Version Independent ID: 0d0bc32b-5909-580f-1030-edbf1d3d9a68
* Content: [Migrate from ASP.NET Web API to ASP.NET Core](https://docs.microsoft.com/en-us/aspnet/core/migration/webapi?view=aspnetcore-6.0&tabs=visual-studio)
* Content Source: [aspnetcore/migration/webapi.md](https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/migration/webapi.md)
* Product: **aspnet-core**
* Technology: **aspnetcore-migration**
* GitHub Login: @ardalis
* Microsoft Alias: **scaddie**