This change defines stages for IR processing. The comments in RazorIRPass
really explain the details. I've also made the preliminary changes to the
stuff we've built so far to follow the new conventions.
This is building towards multitargeting for Razor, being able to target
both Razor Pages and Razor MVC Views from the same engine, being able to
target different codegen and methods from within the same engine.
- Added a common csharp rendering phase base to put shared assets of runtime and design time code gen.
- Added a new `DesignTimeIRPass` to setup the IR bits to provide accurate intellisense.
- Added a `CodeGenerationIntegrationTest` and moved the RuntimeCodeGenerationTests into it. This way we can re-use the cshtml files and it makes searching/running the tests easy..
- Updated how line mappings are calculated for some nodes.
#848