ENH: Use shapefile crs attribute when possible

[greglucas]

When reading in the shapefile, use the .prj file information if it is present to set a crs attribute on the reader which can be used down the line by features to get the correct Projection.

Somewhat interesting that loading the wkt from the file produces a different CRS than the one going through Fiona's CRS first... I'm not sure if that is expected or not, so opening this PR as a draft for now.

closes ##906
closes #2289

[dopplershift]

Seems really odd that those would be different.

[greglucas]

I just pushed an update that puts the same logic into each of the readers so there isn't any difference between FionaReader and BasicReader in how you get a WKT and we rely on pyproj's version to decode the .prj file if it is present.

[dopplershift]

Not sure what's up with CI.

[greglucas]

I'm going to move this back to draft for now so it doesn't get merged.

The docs failures are real and I assume due to an interaction of this new CRS for NaturalEarth and the handling updated in #2455
I can reproduce it with a local docs build, but just running the examples manually as a script works fine. I'm not sure what specific figure size and other options sphinx_gallery uses, but my guess is there is some different settings in there that cause the error to show up.

The other thing I noticed looking through the logs is that we have a lot of UserWarnings now:

UserWarning: Approximating coordinate system <Geographic 2D CRS: GEOGCRS["WGS 84",DATUM["World Geodetic System 1984 ...>
Name: WGS 84
Axis Info [ellipsoidal]:
- lon[east]: Longitude (Degree)
- lat[north]: Latitude (Degree)
Area of Use:
- undefined
Datum: World Geodetic System 1984
- Ellipsoid: WGS 84
- Prime Meridian: Greenwich
 with the PlateCarree projection.

which means that UserWarning gets printed a lot because it is associated with every natural earth feature now.