[SPATIAL] New ShapeFieldMapper for indexing cartesian geometries (#44980)

This commit adds a new ShapeFieldMapper to the xpack spatial module for
indexing arbitrary cartesian geometries using a new field type called shape.
The indexing approach leverages lucene's new XYShape field type which is
backed by BKD in the same manner as LatLonShape but without the WGS84
latitude longitude restrictions. The new field mapper builds on and
extends the refactoring effort in AbstractGeometryFieldMapper and accepts
shapes in either GeoJSON or WKT format (both of which support non geospatial geometries).

Tests are provided in the ShapeFieldMapperTest class in the same manner
as GeoShapeFieldMapperTests and LegacyGeoShapeFieldMapperTests.
Documentation for how to use the new field type and what parameters are
accepted is included. The QueryBuilder for searching indexed shapes is provided in a separate commit.

Author: nknize

docs/reference/mapping/types.asciidoc

@@ -54,6 +54,8 @@ string::         <<text,`text`>> and <<keyword,`keyword`>>
 
 <<flattened>>:: Allows an entire JSON object to be indexed as a single field.
 
+<<shape>>:: `shape` for arbitrary cartesian geometries.
+
 [float]
 [[types-array-handling]]
 === Arrays
@@ -121,4 +123,6 @@ include::types/sparse-vector.asciidoc[]
 
 include::types/text.asciidoc[]
 
-include::types/token-count.asciidoc[]
+include::types/token-count.asciidoc[]
+
+include::types/shape.asciidoc[]

docs/reference/mapping/types/geo-shape.asciidoc

@@ -296,7 +296,7 @@ differs from many Geospatial APIs (e.g., Google Maps) that generally
 use the colloquial latitude, longitude (Y, X).
 =============================================
 
-[[point]]
+[[geo-point-type]]
 [float]
 ===== http://geojson.org/geojson-spec.html#id2[Point]
 
@@ -328,7 +328,7 @@ POST /example/_doc
 // CONSOLE
 
 [float]
-[[linestring]]
+[[geo-linestring]]
 ===== http://geojson.org/geojson-spec.html#id3[LineString]
 
 A `linestring` defined by an array of two or more positions. By
@@ -363,7 +363,7 @@ The above `linestring` would draw a straight line starting at the White
 House to the US Capitol Building.
 
 [float]
-[[polygon]]
+[[geo-polygon]]
 ===== http://www.geojson.org/geojson-spec.html#id4[Polygon]
 
 A polygon is defined by a list of a list of points. The first and last
@@ -480,7 +480,7 @@ POST /example/_doc
 // CONSOLE
 
 [float]
-[[multipoint]]
+[[geo-multipoint]]
 ===== http://www.geojson.org/geojson-spec.html#id5[MultiPoint]
 
 The following is an example of a list of geojson points:
@@ -511,7 +511,7 @@ POST /example/_doc
 // CONSOLE
 
 [float]
-[[multilinestring]]
+[[geo-multilinestring]]
 ===== http://www.geojson.org/geojson-spec.html#id6[MultiLineString]
 
 The following is an example of a list of geojson linestrings:
@@ -544,7 +544,7 @@ POST /example/_doc
 // CONSOLE
 
 [float]
-[[multipolygon]]
+[[geo-multipolygon]]
 ===== http://www.geojson.org/geojson-spec.html#id7[MultiPolygon]
 
 The following is an example of a list of geojson polygons (second polygon contains a hole):
@@ -577,7 +577,7 @@ POST /example/_doc
 // CONSOLE
 
 [float]
-[[geometry_collection]]
+[[geo-geometry_collection]]
 ===== http://geojson.org/geojson-spec.html#geometrycollection[Geometry Collection]
 
 The following is an example of a collection of geojson geometry objects: