[SYCL][NFC] Simplify working with mock images in unit tests#14816

AlexeySachkov merged 2 commits intointel:syclintel/llvm:syclfrom

AlexeySachkov:private/asachkov/mock-image-constructorsAlexeySachkov/llvm:private/asachkov/mock-image-constructorsCopy head branch name to clipboard