When upgrading data nodes to a newer version before
master nodes there was a risk that a transform running
on an upgraded data node would index a document into
the new transforms internal index before its index
template was created. This would cause the index to
be created with entirely dynamic mappings.
This change introduces a check before indexing any
internal transforms document to ensure that the required
index template exists and create it if it doesn't.
Backport of #46553
rename data frame transform plugin to transform:
- rename plugin data-frame to transform
- change all package names from o.e.*.dataframe.* to o.e.*.transform.*
- necessary changes to fix loading/testing