Update dpnp.einsum to align with NEP-50

[vtavana]

In NumPy 2.0 and above, numpy.einsum function follows NEP-50 while in previous version it was not followed.

dpnp.einsum is updated to behave similarly.

New behavior in NumPy and update dpnp on this branch:

import numpy as np
np.__version__
# 2.1.1
a=np.ones(2, dtype=np.float32)
np.einsum(",i->", 3., a)
# np.float64(6.0)

import dpnp
a_dp=dpnp.ones(2, dtype=dpnp.float32)
dpnp.einsum(",i->", 3., a_dp).dtype # on a device with support for double precision
# dtype('float64')

Old behavior in NumPy and dpnp:

import numpy as np
np.__version__
# 1.26.4
a=np.ones(2, dtype=np.float32)
np.einsum(",i->", 3., a).dtype
# dtype('float32')

import dpnp
a_dp=dpnp.ones(2, dtype=dpnp.float32)
dpnp.einsum(",i->", 3., a_dp).dtype
# dtype('float32')

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[github-actions]

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

[antonwolfy]

Thank you @vtavana