[cleanup/tensor, part 4] Made contract_iter and contract_iter2 functions templated to avoid needing to include pybind11 headers

[oleksandr-pavlyk]

Code for contract_iter and contract_iter2 functions in "strided_iters.hpp" used identifiers from ::pybind11 namespace.

Made these functions templated passing necessary types via template parameters.

This is avoid using py::value_error and py::ssize_t and py::type_error in there explicitly.

Use in "tensor_py.cpp" has been adjusted.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/933/index.html

[github-actions]

Array API standard conformance tests for dpctl=0.14.0dev0=py310h8c27c75_180 ran successfully.
Passed: 33
Failed: 801
Skipped: 3138

[oleksandr-pavlyk]

I think this is pretty straightforward commit, so I am going to merge it.

[github-actions]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. 🤞