Made ConversionUtils more robust and cover more of the tensor dialect

[crockeea]

• Added explicit uniform checks for unshaped tensors or tensors with a dynamic shape to robustly limit the coverage of these conversions. Note that ConvertAny still supports dynamic shapes, but it is the only one that does.
• Added support for tensor.from_elements where the output shape is multi-dimensional; previously it only handled the case of a 1D output. Added a test for this case.
• Added support for tensor.extract_slice via ConvertOffsetSizeStrideOp
• Added support for tensor.insert_slice via ConvertOffsetSizeStrideOp
• Added support for tensor.reshape

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[crockeea]

Is CI using BuildBuddy? 42 minutes and counting to validate the PR.