Implements Component code generation and tooling support end to end
udditionally adds some default `@addTagHelper` directives to make
programming in Blazor a little nicer.
Components are discovered as Tag Helpers using Razor's extensibility
during the build/IDE process. This drives the code generation during
build and lights up a bunch of editor features.
Add
This is in preparation for supporting multiple diffs for the same
component in a single batch (which means we can't rely on there being at
most only new render tree per component)
Ryan Nowak
Steve Sanderson