Add new blas extension and update dpnp.matmul func

[vlad-perevezentsev]

This PR updates dpnp.matmul implementation with gemm function call from oneapi::mkl::blas added to dpnp.backend.extensions.blas.
In addition, gemm_batch function is also added which is the batched versions of gemm, performing multiple gemm operations in a single call.
The implementation is written as a pybind11 extension above required BLAS functions.

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[github-actions]

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

[npolina4]

The result does not match with numpy

import numpy, dpnp

def init():
    N = 5
    A = numpy.empty((N, N), dtype=numpy.float32)
    for i in range(N):
        A[i, : i + 1] = numpy.fromfunction(lambda j: (-j % N) / N + 1, (i + 1,))
        A[i, i + 1 :] = 0.0
        A[i, i + 1 :] = 0.0
    return A

def kernel(A):
    for i in range(A.shape[0]):
        for j in range(i):
            A[i, j] -= A[i, :j] @ A[:j, j]

a = init()
b = dpnp.asarray(a)

kernel(a)
kernel(b)
print(a - b.asnumpy())

[[0.  0.  0.  0.  0. ]
 [0.  0.  0.  0.  0. ]
 [0.  0.  0.  0.  0. ]
 [0.  0.  0.  0.  0. ]
 [0.  0.  0.  1.6 0. ]]

[antonwolfy]

Thank you @vtavana !