- part I of #1253 using new Razor capabilities
- update baselines to match latest code generation
- use new `CodeBuilderContext` and `TagHelperAttributeValueCodeRenderer` signatures
- test complex expressions in bound non-string attribute values
- Exposed internals from Mvc.Razor.Host to Mvc.Razor.Test so it can use the MvcRazorHost override that takes the IFileSystem.
- Added end-to-end code generation tests for TagHelpers with ModelExpression properties.
#1241