[BugFix] Handle non-contiguous tensors properly when serializing

[njhill]

Follow-on to #13790. Both msgpack and zmq require contiguous tensors so ensure the tensor is converted in all cases.

Also use a msgpack ext for the inline case to avoid a copy on the decode side.

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[njhill]

Thanks @comaniac! I realized the original PR was wrong though so have updated it and improved the test.