Adds a new `RestInterceptor` interface and converts
`RestServerActionPlugin.getRestHandlerInterceptor` to return this new
type instead of a wrapping function.
This has the following benefits:
- Less object creation, there is 1 instance of the interceptor class
(see `SecurityRestFilter`) rather than an instance per handler
- More control over the sequence of steps in processing a request.
The explicit interceptor separates it from the deprecation handler
or any validation that might be needed, and the controller can be
intentional about the order in which these operations are applied.
This commit renames the tracing to telemetry.tracing in both xpack/APM and elasticserach's org.elasticsearch.tracing.Tracer (the api)
the xpack/APM is renamed as follows:
org.elasticsearch.telemetry.apm - the only exported package
org.elasticsearch.telemetry.apm.settings - APMSettings
org.elasticsearch.telemetry.apm.tracing - APMTracer
org.elasticsearch.tracing.Tracer is moved to org.elasticsearch.telemetry.tracing.Tracer (responsible for majority of the changes in this PR)
This commit changes the ActionModules to allow the RestController to be
provided by an internal plugin.
It renames `RestInterceptorActionPlugin` to `RestServerActionPlugin`
and adds a new `getRestController` method to it.
There may be multiple RestServerActionPlugins installed on a node, but
only 1 may provide a Rest Wrapper (getRestHandlerInterceptor) and only 1
may provide a RestController (getRestController).
