REF: Use pyproj global context instead of the one from PROJ

[snowman2]

• Closes Don't mess with PROJ global context #722

Also connected to #661 and #675

[snowman2]

Hopefully this will be added to 7.2 OSGeo/PROJ#2383 🤞

[snowman2]

Need to test: OSGeo/PROJ#1574

[snowman2]

No core dumping, so it seems okay.

>>> from pyproj import CRS
pyproj/pyproj/__init__.py:78: UserWarning: Valid PROJ data directory not found. Either set the path using the environmental variable PROJ_LIB or with `pyproj.datadir.set_data_dir`.
  warnings.warn(str(err))
>>> from pyproj._datadir import get_global_search_path
>>> get_global_search_path()
b'~/.local/share/proj:~/miniconda/envs/proj4/share/proj'
>>> from pyproj import CRS
>>> CRS(init="epsg:4326")
/home/snowal/scripts/pyproj/pyproj/crs/crs.py:53: FutureWarning: '+init=<authority>:<code>' syntax is deprecated. '<authority>:<code>' is the preferred initialization method. When making the change, be mindful of axis order changes: https://pyproj4.github.io/pyproj/stable/gotchas.html#axis-order-changes-in-proj-6
  return _prepare_from_string(" ".join(pjargs))
/home/snowal/scripts/pyproj/pyproj/crs/crs.py:294: FutureWarning: '+init=<authority>:<code>' syntax is deprecated. '<authority>:<code>' is the preferred initialization method. When making the change, be mindful of axis order changes: https://pyproj4.github.io/pyproj/stable/gotchas.html#axis-order-changes-in-proj-6
  projstring = _prepare_from_string(" ".join((projstring, projkwargs)))
<Geographic 2D CRS: +init=epsg:4326 +type=crs>
Name: unknown
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

[snowman2]

For reference:

def get_global_search_path():
    cdef PJ_INFO info = proj_info()
    searchpath = info.searchpath
    return searchpath