Add prepare rename API

Add an API that will give a response for the VS Code [prepareRename](https://code.visualstudio.com/api/references/vscode-api#RenameProvider) API.
If the location provided is a variable, function or class then rename should be allowed and the API should return the location of the symbol.
If the location provided is not one of the above (e.g. something like `void`, `public`, `static`, a datatype etc.) then undefined/undefined/empty array.