After #53562, the `geo_shape` field mapper is registered within
a module. This opens the door for introducing a new `geo_shape`
field mapper into the Spatial Plugin that has doc-values support.
This is very much an extension of server's GeoShapeFieldMapper,
but with the addition of the doc values implementation.
This commit introduces a new `geo` module that is intended
to be contain all the geo-spatial-specific features in server.
As a first step, the responsibility of registering the geo_shape
field mapper is moved to this module.
Co-authored-by: Nicholas Knize <nknize@gmail.com>