[SYCL][NFC] Move more UR-related declarations into library#15519

AlexeySachkov merged 3 commits intointel:syclintel/llvm:syclfrom

AlexeySachkov:private/asachkov/hide-more-ur-stuff-into-libraryAlexeySachkov/llvm:private/asachkov/hide-more-ur-stuff-into-libraryCopy head branch name to clipboard