Delete unused snippets

[gewarren]

Found these using http://github.com/gewarren/cleanrepo.

[IEvangelist]

I'm not sure how I feel about this PR. The first several files are something that should have been included in related content, I'm addressing that concern in #31757. The next several files were something that I recently added, knowing full well that it wasn't included in the content yet. The idea was that I'd come back to it, and at least have it in dotnet/samples (ideally, want to keep those synched). There are so many files that it's really challenging to ensure that there are more situations like that. I'm torn.

[gewarren]

@IEvangelist I restored the Dockerfile snippets that you added references for in #31757. I've also created a tag (https://github.com/dotnet/docs/releases/tag/snippet-purge-1022) so you can come back and retrieve any snippets that you might need in the future. Also consider adding unreferenced code snippets to the dotnet/samples repo instead.

[IEvangelist]

Looks good to me, when you're ready.