lang: Remove the specialized info structs

Since this was an early form of the modern data struct, remove those and
pass in the correct data. This is also important in case we have
something more complex inside our string interpolation!

lang/structs.go

@@ -4929,13 +4929,25 @@ func (obj *ExprStr) Interpolate() (interfaces.Expr, error) {
 		//Line: -1, // TODO
 		//Filename: "", // optional source filename, if known
 	}
-	info := &InterpolateInfo{
-		Debug: obj.data.Debug,
+
+	data := &interfaces.Data{
+		// TODO: add missing fields here if/when needed
+		Fs:         obj.data.Fs,
+		FsURI:      obj.data.FsURI,
+		Base:       obj.data.Base,
+		Files:      obj.data.Files,
+		Imports:    obj.data.Imports,
+		Metadata:   obj.data.Metadata,
+		Modules:    obj.data.Modules,
+		Downloader: obj.data.Downloader,
+		//World:      obj.data.World,
+		Prefix: obj.data.Prefix,
+		Debug:  obj.data.Debug,
 		Logf: func(format string, v ...interface{}) {
 			obj.data.Logf("interpolate: "+format, v...)
 		},
 	}
-	result, err := InterpolateStr(obj.V, pos, info)
+	result, err := InterpolateStr(obj.V, pos, data)
 	if err != nil {
 		return nil, err
 	}