This commit includes the work that has been done on the runtime fields feature branch until now. The high level tasks are listed in #59332. The tasks that have not yet been completed can be worked on after merging the feature branch.
We are adding a new x-pack plugin called runtime-fields that plugs in a custom mapper which allows to define runtime fields based on a script.
The changes included in this commit that were made outside of the x-pack/plugin/runtime-fields directory are minimal and revolve around 1) making the ScriptService available while parsing index mappings so that the scripts associated to runtime fields can be compiled 2) sharing code to manipulate ranges etc. as it can be reused in runtime fields.
Co-authored-by: Nik Everett <nik9000@gmail.com>
Luca Cavanna