Fix DLPack С-contiguous stride reconstruction

[vlad-perevezentsev]

Previously C-contiguous arrays with ndim > 0 were exported with NULL strides while F-contiguous strides were computed explicitly.
In #2193 NULL strides are no longer allowed due to DLPack v 1.2 and missing strides started to be
computed using only F-order logic so C-contiguous arrays were exported with incorrect strides

import dpctl.tensor as dpt

a = dpt.asarray([[1,2,3],[4,5,6]])
a.strides
# (3, 1)
b = dpt.from_dlpack(a)
b.strides
# (1, 2)

This PR adds stride computation for C-contiguous layouts and resolves #2213

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/2219/index.html

[github-actions]

Array API standard conformance tests for dpctl=0.22.0dev0=py310h93fe807_77 ran successfully.
Passed: 1116
Failed: 42
Skipped: 82

[coveralls]

coverage: 86.25% (-0.02%) from 86.269%
when pulling da72671 on resolve_gh_2213
into 2b3f1ec on master.

[ndgrigorian]

We can define this above with other Cython variables

cdef int flags = 0

which is how it was before the flags check was removed

[ndgrigorian]

good that we're covering this case, I think it would be better to be more specific about the problem though

in dpctl4pybind11.hpp we throw

  throw std::runtime_error("Invalid array encountered when "
                           "building strides");

something like this might make more sense, so it's understood the array is invalid

[ndgrigorian]

same comment as above

[ndgrigorian]

those are the only comments from me, everything else LGTM