TransportNodesAction impls are local-only

[DaveCTurner]

There are no remote invocations of any actions derived from
TransportNodesAction so there is no need to register the top-level
action with the TransportService, and that means that all the code
related to de/serialization of the top-level request and response is
unused and can be removed.

Relates #100111
Relates #100878

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[elasticsearchmachine]

Hi @DaveCTurner, I've created a changelog YAML for you.

[DaveCTurner]

Failure is #99422.

@elasticmachine please run elasticsearch-ci/part-2

[ldematte]

LGTM. Only a couple of Q:

• The only reason BaseNodeRequest has not been changed to TransportAction.localOnly(); is because super() is called from inheritors and it shouldn't. After Do not send full top-level TransportNodesAction request to individual nodes #100878, we can come back and change it, right?
• Is there a place where BaseNodeResponse.readNodesFrom and writeNodesTo are not just TransportAction.localOnly();?

[DaveCTurner]

After #100878 we can come back and change it, right?

Right.

Is there a place where BaseNodeResponse.readNodesFrom and writeNodesTo are not just TransportAction.localOnly();?

Yeah there's a couple of places where the base response is wrapped up in another response that I didn't fancy pulling to bits here, see e.g. org.elasticsearch.xpack.core.analytics.action.AnalyticsStatsAction.Response or org.elasticsearch.xpack.core.spatial.action.SpatialStatsAction.Response, and several more that have nontrivial test suites which I didn't want to unpick here.