[SYCL][Docs] Make external events wait with queue

[steffenlarsen]

This commit adds the behavior to ext_oneapi_set_external_event that it is also waited on when the queue is waited on.

[maarquitos14]

LGTM.

[gmlueck]

Spec changes OK.

[steffenlarsen]

Windows Gen12:

Failed Tests (8):
  SYCL :: Assert/assert_in_kernels_win.cpp
  SYCL :: Assert/assert_in_multiple_tus_one_ndebug_win.cpp
  SYCL :: Assert/assert_in_multiple_tus_win.cpp
  SYCL :: Assert/assert_in_one_kernel_win.cpp
  SYCL :: Assert/assert_in_simultaneous_kernels_win.cpp
  SYCL :: Assert/assert_in_simultaneously_multiple_tus.cpp
  SYCL :: Assert/assert_in_simultaneously_multiple_tus_one_ndebug.cpp
  SYCL :: Plugin/sycl-ls-unified-runtime.cpp

Reported in #12797 and #12798