[SYCL][Graph] Fix memory leaks in new graph tests

[maarquitos14]

Fix memory leaks in newly added graph tests in #12433.

[maarquitos14]

@mfrancepillois FYI.

[EwanC]

Thanks for catching this

[EwanC]

tagging @intel/llvm-gatekeepers for merging

[aelovikov-intel]

Post commit failures (for future references/searches):

# Arc GPU:
Failed Tests (2):
  SYCL :: Basic/get_backend.cpp
  SYCL :: USM/usm_pooling.cpp

The first one is known and has been addressed since (IIRC), the second failed like this:

# RUN: at line 22
env UR_L0_DEBUG=1 SYCL_PI_LEVEL_ZERO_USM_RESIDENT=0 SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR=";2M;2M,4,64K" env ONEAPI_DEVICE_SELECTOR=level_zero:gpu  /__w/llvm/llvm/build-e2e/USM/Output/usm_pooling.cpp.tmp.out h 2>&1 | /__w/llvm/llvm/toolchain/bin/FileCheck /__w/llvm/llvm/llvm/sycl/test-e2e/USM/usm_pooling.cpp --check-prefix CHECK-1245
# executed command: env UR_L0_DEBUG=1 SYCL_PI_LEVEL_ZERO_USM_RESIDENT=0 'SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR=;2M;2M,4,64K' env ONEAPI_DEVICE_SELECTOR=level_zero:gpu /__w/llvm/llvm/build-e2e/USM/Output/usm_pooling.cpp.tmp.out h
# note: command had no output on stdout or stderr
# executed command: /__w/llvm/llvm/toolchain/bin/FileCheck /__w/llvm/llvm/llvm/sycl/test-e2e/USM/usm_pooling.cpp --check-prefix CHECK-1245
# note: command had no output on stdout or stderr
# RUN: at line 23
env UR_L0_DEBUG=1 SYCL_PI_LEVEL_ZERO_USM_RESIDENT=0 SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR=";2M;2M,4,64K" env ONEAPI_DEVICE_SELECTOR=level_zero:gpu  /__w/llvm/llvm/build-e2e/USM/Output/usm_pooling.cpp.tmp.out d 2>&1 | /__w/llvm/llvm/toolchain/bin/FileCheck /__w/llvm/llvm/llvm/sycl/test-e2e/USM/usm_pooling.cpp --check-prefix CHECK-1245
# executed command: env UR_L0_DEBUG=1 SYCL_PI_LEVEL_ZERO_USM_RESIDENT=0 'SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR=;2M;2M,4,64K' env ONEAPI_DEVICE_SELECTOR=level_zero:gpu /__w/llvm/llvm/build-e2e/USM/Output/usm_pooling.cpp.tmp.out d
# note: command had no output on stdout or stderr
# error: command failed with exit status: -6
# executed command: /__w/llvm/llvm/toolchain/bin/FileCheck /__w/llvm/llvm/llvm/sycl/test-e2e/USM/usm_pooling.cpp --check-prefix CHECK-1245
# note: command had no output on stdout or stderr