MAINT: Move to new numpy.random API in test_*.py

[MridulS]

This PR is another go at #12669 and this builds on top of #13747. With this PR we can start addressing #11687

This PR does not make any API changes! This just edits the tests file to update them to the old numpy random generator API.

There is a ruff numpy rule, so I am trying to make it happy here. For certain tests I had to play around with seeds, atol/rtol. I still need to work a bit more on this.

Once this is in we can start looking at adding arguments to expose numpy RNG instance for functions that depend on internal random state. Once this is in we can also start deprecating NumpyRNGContext.

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[pllim]

Out of scope here but I just want to link for future self... #11566

[nstarman]

@MridulS, what if you defined a rng fixture in the main conftest.py, then you can just add an rng argument to any pytest function to get the rng. Should save a lot of lines!

[nstarman]

LGTM for units. However, see my other comment for a way to simplify all the tests using a rng pytest fixture.