LazyLoadingReadOnlyStream.Position setter not implemented while Seek is

[twsouthwick]

Describe the bug
I often use the Stream.Position property to set position on seekable streams. With the recent changes to enable seekability (#15032), we can now call Stream.Seek(..., SeekOrigin), but .Position fails.

Expected behavior
I would expect calls to .Position = x to work similarly to .Seek(x, SeekOrigin.Begin) as they do on other streams.

Actual behavior (include Exception or Stack Trace)
Throws NotSupportedException

To Reproduce
Steps to reproduce the behavior (include a code snippet, screenshot, or any additional information that might help us reproduce the issue)

var client = _container.GetBlobClient(plateName);
var stream = client.OpenRead();
stream.Position = 0;

Environment:

• Name and version of the Library package used: Azure.Storage.Blobs 12.7.0-alpha.20201016.1
• Hosting platform or OS and .NET runtime version (dotnet --info output for .NET Core projects): .NET Framework 4.8
• IDE and version : Visual Studio 16.7.5

[twsouthwick]

@seanmcc-msft

[jsquire]

Thank you for your feedback. Tagging and routing to the team best able to assist.

[ghost]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @xgithubtriage.

[seanmcc-msft]

@twsouthwick I can reproduce this issue, and we will have a fix out soon.