CVE-2022-23582: `CHECK`-failures in `TensorByteSize` in Tensorflow

A malicious user can cause a denial of service by altering a SavedModel such that TensorByteSize would trigger CHECK failures.

int64_t TensorByteSize(const TensorProto& t) {
// num_elements returns -1 if shape is not fully defined.
int64_t num_elems = TensorShape(t.tensor_shape()).num_elements();
return num_elems < 0 ? -1 : num_elems * DataTypeSize(t.dtype());
}

TensorShape constructor throws a CHECK-fail if shape is partial or has a number of elements that would overflow the size of an int. The PartialTensorShape constructor instead does not cause a CHECK-abort if the shape is partial, which is exactly what this function needs to be able to return -1.