render: unify getter for texture formats
Instead of having separate getters for shm formats and DMA-BUF formats, use the same pattern as wlr_output_impl.get_primary_formats with a single function which takes buffer caps as input.
Instead of having separate getters for shm formats and DMA-BUF formats, use the same pattern as wlr_output_impl.get_primary_formats with a single function which takes buffer caps as input.