Prioritize hgln_obs over crln_obs when extracting observer information from FITS headers

[svank]

Fix as proposed in #7184

Thanks @ayshih for confirming this should be right!

[dstansby]

Looks 👍 , just one request for a comment, and needs a bugifx changelog entry adding.

[svank]

@dstansby Thanks! I've made these changes.

[ayshih]

Some text edits, otherwise looks good to me!

If I were to be super-picky, the part of the unit test that tests the prioritization in the Map implementation should really live under sunpy.map.tests and not sunpy.coordinates.tests, because the relevant code – how GenericMap prioritizes and sanitizes the observer location – all lives in sunpy/map/mapbase.py.

[ayshih]

Suggested change

	Ensure that when instantiating a `WCS` from a FITS Header, the observer location is set from the Stonyhurst coordinates rather than the Carrington coordinates when both are present.
	When directly instantiating a `~astropy.wcs.WCS` from a FITS header that contains both Stonyhurst and Carrington heliographic coordinates for the observer location, the Stonyhurst coordinates will now be prioritized.
	This behavior is now consistent with the `~sunpy.map.Map` class, which has always prioritized Stonyhurst coordinates over Carrington coordinates.

[ayshih]

Suggested change

	Going through `Map` and `WCS` seem to follow (at least slightly) different
	code paths, so test them both.
	`Map` creates a custom FITS header with a sanitized observer location, so
	we need to also test a directly instantiated `WCS` object.

[Cadair]

the part of the unit test that tests the prioritization in the Map implementation should really live under sunpy.map.tests

Given my recent foray into seeing if it's possible to run tests for subpackages without optional dependencies installed, ideally we would not have a direct reliance on map in the coordinates tests.

Changes addressed

[svank]

What's code review for, if not being picky? I moved the Map part of the test to the map module---there is still a pre-existing Map dependence in coordinates/tests/test_wcs_utils.py, but now I avoid further entrenching that.

Text edits are also implemented.

[ayshih]

Looks good to me!

[ayshih]

Thanks, @svank!