Remove StreamWrapper workaround that does sync-over-async

We have a StreamWrapper workaround in the library that wraps around he response stream, intercepts calls to synchronous I/O and calls asynchronous I/O with Wait() or Result, e.g. Flush() calls FlushAsync().Wait(): https://github.com/OData/AspNetCoreOData/blob/c2b19f365cc650ce8140fb9f9ab9a61bb0f426d8/src/Microsoft.AspNetCore.OData/Formatter/ODataOutputFormatterHelper.cs#L244

The purpose of this wrapper is to work around the fact that ASP.NET Core by default does not allow synchronous I/O, but ODataMessageWriter and CsdlWriter have cases where they perform synchronous I/O in async code. However, this workaround can cause more harm than even having synchronous I/O since it would lead to blocking two threads where synchronous code would have blocked one. See: https://github.com/davidfowl/AspNetCoreDiagnosticScenarios/blob/master/AsyncGuidance.md#avoid-using-taskresult-and-taskwait

Since we have recently prioritized removing synchronous I/O in ODL's async APIs, we should also remove this workaround and fix any sync I/O errors that keep us from removing this workaround.

Start in src/Microsoft.AspNetCore.OData/Formatter/ODataOutputFormatterHelper.cs around the StreamWrapper implementation and review the ODataMessageWriter and CsdlWriter async paths. Identify the synchronous I/O errors that prevent removal, then verify that the workaround is gone and those async paths no longer require it.