Reduce memory consuption in axis_world_coords (again)

[Cadair]

This PR works, as an alternative to #780 by not generating mesh coords for unneeded pixel axes.

i.e. if the pixel axes are not correlated with a requested world axis then don't generate the coords in the mesh.

[Cadair]

This PR needs tests which test at least with some DKIST or IRIS WCSes that you can get low-memory axis world coords for uncorrelated axes, and as a counterpoint that correlated axes still work properly.

For example, I have tested that axis_world_coords("time") works fine for this dataset but not that axis_world_coords("lat") works for instance (which should still generate a large grid).

[nabobalis]

I do question why I bother to do any programming if its always wrong.

This solution works:

Command line: /home/nabil/.mamba/envs/iris-dev/bin/memray run -f -o output.bin examples/umbral_flashes.py
Start time: Tue Dec 17 2024 11:08:16 GMT-0800 (Pacific Standard Time)
End time: Tue Dec 17 2024 11:08:42 GMT-0800 (Pacific Standard Time)
Duration: 0:00:26.707000
Total number of allocations: 6674037
Total number of frames seen: 17921
Peak memory usage: 2.3 GiB
Python allocator: pymalloc

The biggest allocations are from loading the data:

[DanRyanIrish]

This is great news!

[Cadair]

@nabobalis I can't add a visp WCS without a dkist dependency, I assume you can't either?

[nabobalis]

@nabobalis I can't add a visp WCS without a dkist dependency, I assume you can't either?

I am the same

[nabobalis]

Could we try Wills WCS from his issue?

[nabobalis]

Not sure if this is good.

[Cadair]

I would be nice to get a test which tests the 2D usecase.

[nabobalis]

How does one do that?