[UR][L0] Possible memory leak in `ur_buffer::getBufferZeHandle`

[AlexeySachkov]

There are many other places in the function which have the same issue, but I will use the following snippet to illustrate it:

llvm/unified-runtime/source/adapters/level_zero/memory.cpp

Lines 2101 to 2124 in 635c62a

	ur_ze_event_list_t waitlist;
	waitlist.ZeEventList = nullptr;
	waitlist.Length = 0;
	uint32_t EventListIndex = 0;
	for (unsigned i = 0; i < numWaitEvents; ++i) {
	if (phWaitEvents[i]->HostVisibleEvent) {
	ZE2UR_CALL(zeEventHostSynchronize,
	(phWaitEvents[i]->ZeEvent, UINT64_MAX));
	} else {
	// Generate the waitlist for the Copy calls based on the passed in
	// dependencies, if they exist for device only.
	if (waitlist.ZeEventList == nullptr) {
	waitlist.ZeEventList = new ze_event_handle_t[numWaitEvents];
	}
	waitlist.ZeEventList[EventListIndex] = phWaitEvents[i]->ZeEvent;
	waitlist.Length++;
	EventListIndex++;
	}
	}
	if (waitlist.Length > 0) {
	ZE2UR_CALL(zeCommandListAppendWaitOnEvents,
	(UrContext->ZeCommandListInit, waitlist.Length,
	waitlist.ZeEventList));
	}

The problem is that every time we do ZE2UR_CALL, it may do plain return from the function if error is encountered. If that happens, memory allocated in waitlist.ZeEventList is not deallocated.

This issue was discovered by the Coverity, its CID is 520798