Add function to load Black Marble dataset

[weiji14]

Description of proposed changes

Function to load the @earth_night_ NASA Black Marble mosaic RGB images stored as GeoTIFF files.

Preview at https://pygmt-dev--3469.org.readthedocs.build/en/3469/api/generated/pygmt.datasets.load_black_marble.html

Example usage:

import pygmt

image = pygmt.datasets.load_black_marble(resolution="06m")

fig = pygmt.Figure()
fig.grdimage(grid=image)
fig.show()

produces

Implementation is adapted from #2235.

Fixes #1442, supersedes #1457

Reminders

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• Add tests for new features or tests that would have caught the bug that you're fixing.
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• If adding new functionality, add an example to docstrings or tutorials.
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[weiji14]

This line is not covered by a unit test. Should I add one, or we can ignore it?

[seisman]

It should be covered when rioxarray is installed, right?

[seisman]

Or do we have to import rioxarray to register the rio accessor

[weiji14]

The equivalent line in load_blue_marble is covered here in test_grdimage_image.py which has an import rioxarray at the top of the file:

pygmt/pygmt/tests/test_grdimage_image.py

Line 18 in 66f258a

xr_image = load_blue_marble(resolution="01d")

We don't test load_black_marble anywhere else except in test_datasets_earth_night.py, and since rioxarray is not imported in that file, this line isn't covered because there is no rio accessor.

[weiji14]

Maybe we can cover this line in the test_grdcut_image.py file at https://github.com/GenericMappingTools/pygmt/pull/3115/files#r1780370539?

[seisman]

since rioxarray is not imported in that file, this line isn't covered because there is no rio accessor.

This is not ideal. So even if rioxarray is installed, the rio accessor may still not exist because users don't import the rioxarray package.

I think we should add the following lines to this file (and any other files that try to access the rio accessor):

pygmt/pygmt/datasets/tile_map.py

Lines 21 to 23 in 66f258a

	with contextlib.suppress(ImportError):
	# rioxarray is needed to register the rio accessor
	import rioxarray # noqa: F401

[seisman]

xref: #3323

[weiji14]

Ok, done at commit 66183ed. I've also applied this to pygmt/datasets/earth_day.py, hopefully you don't mind.

[seisman]

Alos need to add earth_night_01d to caching.py