Issue Description:

A refactoring action that automated turning a tuple-typed declaration into a struct would be useful, since it's common to "outgrow" a tuple and need the features of a named struct type. If you could point at a tuple-typed variable, argument, or return type, and ask the refactoring engine to replace it with a struct type, ideally with a choice to either use an existing one or create a new struct declaration too, it could update the declaration and automatically map any tuple literal/element expressions to the equivalent struct initializer/property expressions.