Expose adding files and folders in sql database projects (#14391)

* expose addToProject in dataworkspace.d.ts

* remove changes in data workspace extension

* add sqldbproj.d.ts

* change list to be Uris instead of strings

* don't add files/folders if any don't exist

* fix test on windows

extensions/sql-database-projects/src/common/constants.ts

@@ -170,6 +170,7 @@ export const externalStreamingJobValidationPassed = localize('externalStreamingJ
 export function projectAlreadyOpened(path: string) { return localize('projectAlreadyOpened', "Project '{0}' is already opened.", path); }
 export function projectAlreadyExists(name: string, path: string) { return localize('projectAlreadyExists', "A project named {0} already exists in {1}.", name, path); }
 export function noFileExist(fileName: string) { return localize('noFileExist', "File {0} doesn't exist", fileName); }
+export function fileOrFolderDoesNotExist(name: string) { return localize('fileOrFolderDoesNotExist', "File or directory '{0}' doesn't exist", name); }
 export function cannotResolvePath(path: string) { return localize('cannotResolvePath', "Cannot resolve path {0}", path); }
 export function fileAlreadyExists(filename: string) { return localize('fileAlreadyExists', "A file with the name '{0}' already exists on disk at this location. Please choose another name.", filename); }
 export function folderAlreadyExists(filename: string) { return localize('folderAlreadyExists', "A folder with the name '{0}' already exists on disk at this location. Please choose another name.", filename); }