sycl: use async memory allocation to fix crashes during graph recording (llama/16644)

sycl: use async memory allocation to fix crashes during graph recording (llama/16644)

* sycl: use async memory allocation to fix graph recording failures

GGML_SYCL_DISABLE_GRAPHS=0 causes crashes because:
  - Host waits are currently unsupported in graph recording mode.
  - SYCL malloc / free calls are unsupported in graph recording mode.

The following changes are made to fix SYCL graph functionality:
  - When graphs are enabled, use the SYCL async memory extension for temp
    buffers which is supported with SYCL graphs.
  - For compiler versions that do not support this extension, skip
    graphs with the affected op.
  - Switch from USM shared to device memory as the async extension
    currently just supports device allocations.

* Address reviewer feedback

* Use global async variable to decide path in sycl_ext_[malloc_device|free]