[SYCL] Implement SYCL_INTEL_enqueue_barrier DPC++ extension

[dm-vodopyanov]

This patch adds the implementation of SYCL_INTEL_enqueue_barrier DPC++ extension.

There are situations where defining dependencies based on events is more explicit than desired or required by an application. For instance, the user may know that a given task depends on all previously submitted tasks. Instead of explicitly adding all the required handler::depends_on calls, the user could express this intent via a single call, making the program more concise and explicit.

To simplify the interface, this extension adds two new members to the handler class, and two new members to the queue class:

handler::barrier : void barrier() and void barrier(const vector_class<event> &WaitList)
queue::submit_barrier : event submit_barrier() and event submit_barrier(const vector_class<event> &WaitList)

[dm-vodopyanov]

Also enqueue_barrier LIT test should be either updated with L0 support after merging PR #1839 as part of this PR (or as separate PR), or this test should be updated in #1839 if this PR (#1836) will be merged before merging #1839.
FYI @againull

[dm-vodopyanov]

It's Segmentation fault (core dumped) using L0 on zeCommandListAppendBarrier func call (I'm investigating this) and a non-related issue in LIT test, so please don't merge yet.

Upd: not on zeCommandListAppendBarrier func call, it's on ze_event_handle_t ZeEvent = (*Event)->ZeEvent; line.

[dm-vodopyanov]

@smaslov-intel I fixed segmentation fault in piEnqueueEventsWaitWithBarrier implementation for Level Zero, now feature works fine with it. Plus fixed a separate issue in LIT test. Could you please re-review?

@jbrodman could you review, please?

[againull]

Also enqueue_barrier LIT test should be either updated with L0 support after merging PR #1839 as part of this PR (or as separate PR), or this test should be updated in #1839 if this PR (#1836) will be merged before merging #1839.
FYI @againull

Thank you very much for taking this into account!

[bader]

@dm-vodopyanov, please, update your branch to fix the pre-commit tests.

[dm-vodopyanov]

@bader Thanks! Updated.

[jbrodman]

LGTM