[Tooling] Changed TagHelper attributes to be SpanKind.Code if not string typed.

- Also added tests to validate that non string TagHelper attributes inherit the SpanKind.COde behavior.
- Removed a block wrapping around single markup spans.

/cc @pranavkm 
I'm not sure how we determine the `attributeTypeName` to start with, but is it a value that the user types in? For instance, it prevents the user from saying `string', `String` etc and specifically use `System.String`.