When code-gening inherited chunks that replace TModel token, wrap it in line pragmas

[pranavkm]

As part of directive inheritance from _GlobalImports, we perform a string replacement on certain kinds of chunks to change the token TModel real model type. For e.g., GlobalImport might contain @inject IFoo<TModel> MyFoo which gets code-gened as public IFoo<MyRealModel> MyFoo { get; set; }.

We should instead code-gen this with line pragmas as

public IFoo<
#line 23 something.cshtml
MyRealModel
#line hidden
> { get; set; }

This will ensure errors related to MyRealModel (misspelt type name etc) map to the view file correctly.

[pranavkm]

@NTaylorMullen and I looked at this as part of 89f58aa and discovered line mappings need to be above full statements and wrapping partial lines like this generally gets ignored. We made some changes as to how the @model gets code gened as part of ff4100e so design time mappings continue working correctly.