HTTP/3: Refactor to use HttpConnnection (#32238)

...rs/Kestrel/Core/src/Internal/BaseHttpConnectionContext.cs

...ers/Kestrel/Core/src/Internal/Http/Http1OutputProducer.cs

...rvers/Kestrel/Core/src/Internal/Http2/Http2FrameWriter.cs

...ervers/Kestrel/Core/src/Internal/Http3/Http3Connection.cs

src/Servers/Kestrel/Core/src/Internal/Http3/Http3Stream.cs

src/Servers/Kestrel/Core/src/Internal/HttpConnection.cs

...ervers/Kestrel/Core/src/Internal/HttpConnectionContext.cs

...rel/Core/src/Internal/HttpMultiplexedConnectionContext.cs

src/Servers/Kestrel/Core/src/Internal/KestrelServerImpl.cs

...el/Core/src/Middleware/HttpConnectionBuilderExtensions.cs

...ore/src/Middleware/HttpMultiplexedConnectionMiddleware.cs

src/Servers/Kestrel/shared/test/TestContextFactory.cs

...trel/test/InMemory.FunctionalTests/Http3/Http3TestBase.cs