update_argsort_test

[vtavana]

In this PR, a few test related to dpnp.argsort are updated.

dpnp.argsort output is always "stable" (which means the returned indices must maintain the relative order of input values which compare as equal) but for NumPy its not necessary "stable".
In the updated tests, random floating numbers are generated, and when their data type is changed to integer type to align with requested data type of the test, we may encounter with repetitive numbers in the input array for which "stable" condition plays a role.
"stable" flag is added to the tests to make sure NumPy also always returns the stable result.

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[github-actions]

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

[antonwolfy]

Thank you @vtavana for resolving that!