Add dpnp.linalg.solve() function

[vlad-perevezentsev]

This PR adds a missing dpnp.linalg.solve() function to calculate the solution to the system of linear equations with a square coefficient matrix A and multiple right-hand sides using oneapi::mkl::lapack::gesv
The implementation is written as a pybind11 extension above required LAPACK functions.

import dpnp

a = dpnp.array([[1, 2], [3, 5]])
b = dpnp.array([1,2])

dpnp.linalg.solve(a,b)
# array([-1.,  1.])

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/index.html

[antonwolfy]

I have a minor comment only, which can be addressed later.
Overall LGTM! Thank you @vlad-perevezentsev