Fix create BitmapDecoder with async file stream.

[lindexi]

Fixes Issue #4355

Description

Fix #4355

Customer Impact

Regression

Testing

Just CI and my demo: https://github.com/lindexi/lindexi_gd/tree/20b78c5547b2ecacdd244a438ef58518469a91d7/GeafakaijawkeheahemLejeehocear

Risk

[lindexi]

Ping @vishalmsft

[vishalmsft]

Thank you @lindexi for the PR. The fix looks to work, as discussed in the relevant issue.
Can you please also submit a Test case at wpf-test

Please let me know, if you need any help with adding the test there. It is just about adding one new WPF project and then adding the executable entry in the xml file.
In case more help is needed, feel free to create one discussion \ Q&A entry.

[lindexi]

@vishalmsft Thank you. And I added the Test case in dotnet/wpf-test#14

But I need your help reviewing my test code.

[dipeshmsft]

We have taken this PR for the current Community Test Pass. Thanks for the contribution.

[lindexi]

Thank you @dipeshmsft

And can you review my test PR: dotnet/wpf-test#14

[dipeshmsft]

Regarding the test PR, we would have to wait for a little. The test may need to be in a different area ( the tests are divided into areas and subareas ), so once, we have all the areas there ( only a few DRTs are remaining ), we will have a discussion on that and go ahead with the test PR.

[lindexi]

Thank you @dipeshmsft