[UR] Add generated lit files to the `LLVM_LIT_CONFIG_FILES` list (#18776)
This list is used in `llvm-lit` to map source configs to their generated
versions. This enables the use of `llvm-lit path/to/test/source/file`
e.g. `llvm-lit
~/dpcpp/unified-runtime/test/adapters/level_zero/confirm_version.cpp`