DOC: update user manual for functions that ~moved from shapely.ops to shapely

[theroggy]

From shapely 2.0, many functions that were in shapely.ops before, became available directly in the shapely namespace, I suppose in the spirit of Flat is better than nested. Some functions were also renamed to be more consistent with GEOS/PostGIS.

However, the user manual wasn't updated to reflect this. This PR tries to incorporate these changes.

I expected this to be a mainly cosmetic change, but while making the changes I encountered many more differences between the functions than I was expecting, so to be discussed how to deal with this:

• line-like input versus explicit iterables of Linestrings: line oriented functions in shapely.ops support line-like input, but the equivalent functions in shapely don't . I changed the doc to reflect that, but maybe this is not wanted? Relevant functions:
  • shapely.ops.polygonizevsshapely.polygonize`
  • shapely.ops.polygonize_full vs shapely.polygonize_full
• shapely.line_merge is a vectorized function and expects a (arraylike of) MultiLineStrings as input. Hence, many merge operations can be done in one call. shapely.ops.linemerge expects an iterable of line-line elements as input, and will merge those, so only one merge operation can be done per call.
• some functions return slightly different results, e.g.:
  • shapely.shortest_line returns a LineString vs shapely.ops.nearest_points returns a Tuple of 2 Points