Deprecate chunk_polygon and promote apply_polygon

[soxofaan]

see Open-EO/openeo-processes#287, Open-EO/openeo-processes#298 where apply_polygon was introduced, based on original chunk_polygon proposal.

We should

• introduce standard apply_polygon
• deprecate non-standard chunk_polygon (e.g. avoid usage in examples, tutorials, docs, ...)

[soxofaan]

FYI: under #195 I already added apply_polygon (aliased by chunk_polygon) as part of larger task (openeo-process v2 update) in 82e264b

still to be done:

• verify that apply_polygon and chunk_polygon can be implemented as as aliases, or implementation should be split up
• port examples and use cases as much as possible to apply_polygon as chunk_polygon is a dead end and we should not promote its usage

[soxofaan]

related:

• apply_polygon (previously known as chunk_polygon) abuses MultiPolygon as collection of polygons in its internal API #288