[SYCL][L0] Fix memory leak in USM prefetch

[bso-intel]

L0 plugin increments the ref count of the dependency event twice in USM prefetch.
The fix is to remove the unnecessary retain call.

[bso-intel]

We already call createAndRetainPiZeEventList for the EventWaitList at line 7313 below.
This code unnecessarily increment the reference count twice, which leads to memory leak.

[smaslov-intel]

In all other cases we create TmpWaitList before creating the real Event (and I don't remember why now). Please investigate/document and make your change in line with the rest of the code (presumably remove the other call to createAndRetainPiZeEventList, not this one)

[smaslov-intel]

In all other cases we create TmpWaitList before creating the real Event (and I don't remember why now). Please investigate/document and make your change in line with the rest of the code (presumably remove the other call to createAndRetainPiZeEventList, not this one)

[bso-intel]

@smaslov-intel ,
Actually, it is better to keep line 7313 than this removed code.
Later when we need to cleanup the events in WaitList.collectEventsForReleaseAndDestroyPiZeEventList(EventsToBeReleased), we need the length of the ref-count-incremented events to call piEventRelease() properly.
This length of the ref-count-incremented events was set in TmpWaitList.createAndRetainPiZeEventList() on the TmpWaitList.
By keeping line 7313, we keep this length on the EventWaitList properly.

[smaslov-intel]

See #3081 for why createAndRetainPiZeEventList is needed before command-list is allocated.

[bso-intel]

Thanks @smaslov-intel.
I fixed as you requested.

[bso-intel]

Hold the review. It seems it is mixed up with some other changes.

[smaslov-intel]

Hold the review. It seems it is mixed up with some other changes.

Yes, please update. And please also add comment to createAndRetainPiZeEventList that it must be run before a subsequent getAvailableCommandList so that there is no dead-lock from waiting unsubmitted events in an open batch.

[bso-intel]

Ok. Now it shows the correct changeset.
I added the comment, too.