Add `StringTensorUnpack-15` and `StringTensorPack-15` to Core (#25606) #8

Job	Run time
Smart_CI	22s
Docker	1s
Build	0s
Debian Packages	0s
OpenVINO JS API	0s
Samples	0s
Conformance	0s
ONNX Runtime Integration	0s
CPU functional tests	0s
C++ unit tests	0s
ONNX Models Tests	0s
Python unit tests	0s
dGPU Tests	0s
iGPU Tests	0s
NVIDIA plugin	0s
OpenVINO tokenizers extension	0s
TensorFlow Models tests	0s
TensorFlow Layer Tests	0s
TensorFlow TF Hub Models tests	0s
TensorFlow Hugging Face Models tests	0s
PyTorch Models tests	0s
PyTorch Models Nightly Scope1 tests	0s
PyTorch Models Nightly Scope2 tests	0s
ci/gha_overall_status	1s
	24s

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