In #81809 we introduced a mechanism to check searializability of search request
to earlier version nodes already on the coordinating node. This requires
knowledge about the version that NamedWritable classes have been introduced,
which is why we started moving classes that are used inside the search request
under the VersionedNamedWriteable interface to make sure future additions
implement the mthod that provides the version information.

This change moves pipeline aggregation builders under that interface. Most builders
have been around long before version 7.0, so we return an empty version tag for them.
The newer ones return the version they were first released in.