Use numpy.testing.assert_allclose for more consistent floating-point comparisons

[agriyakhetarpal]

Currently, we use np.testing.assert_array_almost_equal in 404 places across 41 files, but the NumPy authors no longer recommend it. We should switch to the recommended np.testing.assert_allclose testing method where we can (which can be in one PR or multiple PRs), across all our tests.

Please note that there are a few differences in the number of arguments both functions take and in the default tolerance(s) set for them, so it's not a quick swap and some failures could be expected – but it should still be easy for someone to take it up in parts.

[Saransh-cpp]

Also, all the instances of assert all(numpy_array == numpy_array)/assert np.allclose(numpy_array == numpy_array) (if we have any) should be replaced with numpy.testing calls.

[mukulbindal]

Hi @Saransh-cpp @agriyakhetarpal If no one is working on this issue, kindly assign this to me.

[arjxn-py]

Hi @mukulbindal, thanks for showing your interest. Feel free to pick this up and do let us know in case you need help :)

[agriyakhetarpal]

Hi @mukulbindal, how is this coming along? Here's our guide in case you're not comfortable with contributing yet and if you need more instructions to follow along: https://docs.pybamm.org/en/latest/source/user_guide/contributing.html

[mukulbindal]

@agriyakhetarpal I got some personal emergency so I parked this task. I'll start on this now.