Added snippets for conditional logical operators

[pkulikov]

Supports dotnet/docs#8880

[pkulikov]

I think a new example is a more obvious demonstration of the evaluation of the second operand. I've checked: such a snippet runs fine as an interactive code snippet.

[rpetrusha]

Thanks for moving the examples to the dotnet/samples repo, @pkulikov, and creating replacing the first example with a more intuitive one. I'll merge your PR and rebuild the article in dotnet/docs.