Add more tests to parse GeoTIFFs with custom CRSes

A GeoTIFF can be defined by either an integer EPSG code or by a custom CRS description.

The integer EPSG code is a very simple case. We can just pass the EPSG code to `pyproj.CRS.from_epsg`.

The custom CRS is more difficult to parse. In #16 we're adding an implementation partially written by Claude. We have one test, using https://github.com/developmentseed/geotiff-test-data/pull/16 as the data file.

It would be great to add more tests for more sorts of images that are defined by a custom CRS.

### Tasks

- [ ] Find more COGs defined by custom CRS (not by EPSG code). Or create some from scratch.
- [ ] Add more such COGs to geotiff-test-data
- [ ] Add these test paths to the pytest parameterizations in `test_crs.py`

FYI: when a COG is not defined by an EPSG code, the CRS field in `rio cogeo info` is a full WKT2 string: https://github.com/developmentseed/geotiff-test-data/blob/0224b1c522d9b32a37b4b95fe92298b9a0f38f2b/real_data/nlcd/nlcd_landcover_info.md?plain=1#L24