MatFileUpload without the need for MemorySteam

[mdeeken]

Describe the feature request
Currently when we want to use the MatFileUpload Component and get the content of the file in order to upload it to a server do do something else with it, we need to write it to a MemoryStream. Besides Problem with filesizes bigger than 50 MB (see #879), using MemoryStreams is discouraged from Microsoft (https://docs.microsoft.com/de-de/aspnet/core/blazor/file-uploads?view=aspnetcore-5.0).

Expected behavior
Read the file content with something else like StreamReader.

[Christian-Oleson]

@mdeeken ,

Thanks for the report! Would you mind opening a PR for this issue?