Updated Tensorflow.Net to 0.70.2 with Tensorflow 2.7.0.

[Crichen]

Fixes #7471

NumSharp replaced with Tensorflow.NumPy.
TensorShape replaced with Shape, Shape object has dimensions as 64 bit long, check added for casting to 32 bit int alsoTensor constructor using SafeTensorHandle/DangerousGetHandle and TF_DataType not required when casting.

Added StringTensorFactory to wrap addition tensorflow.dll methods required to create Tensors from string based input.

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[Crichen]

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[Crichen]

CI failing is interesting, I wonder if the dotnet9.0 runtime needs to be included in the initial build steps?
Following the standard build process: 6.0.36, 8.0.16 and 10.0.0-preview.3.25171.5 are installed to the machinelearning\.dotnet folder. Running .\build.cmd -test -integrationTest resulted in errors with referencing 9.0.

I installed the runtime manually to the machinelearning\.dotnet location and this was then resolved. Very unsure of where in the tooling pipeline this would need to be updated.