Implemented dpctl.tensor.linspace per array API

[oleksandr-pavlyk]

This PR implements dpctl.tensor.linspace as per array-API specification.

In [1]: import dpctl.tensor as dpt

In [2]: dpt.asnumpy(dpt.linspace(0, 3 + 3j, num=4))
Out[2]: array([0.+0.j, 1.+1.j, 2.+2.j, 3.+3.j])

In [3]: dpt.asnumpy(dpt.linspace(0, 3 + 3j, num=5, endpoint=False))
Out[3]: array([0. +0.j , 0.6+0.6j, 1.2+1.2j, 1.8+1.8j, 2.4+2.4j])

In [4]: dpt.asnumpy(dpt.linspace(0, 3 + 3j, num=3, endpoint=False))
Out[4]: array([0.+0.j, 1.+1.j, 2.+2.j])

In [5]: dpt.asnumpy(dpt.linspace(0, 3, num=3, endpoint=False))
Out[5]: array([0., 1., 2.])

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/875/index.html

[coveralls]

Coverage increased (+0.04%) to 81.859% when pulling 01b6cc1 on add-linspace into da1bf68 on master.

[github-actions]

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