- Map transaction.duration.us independently of span.duration.us,
  fix ingest pipeline. We might consider aliasing later.
- Set event.ingested
- Set processor.event, using constant_keyword where possible

…eams

See elastic#96267 (comment)

- Index templates have a "@template" suffix
- Component templates are split into settings and mappings,
  and have a @settings and @mappings suffix respectively
- Ingest pipelines generally have a @pipeline suffix,
  except for one special case where we use @default-pipeline

We no longer have a component template for every data stream, rather we
have reusable component templates where it makes sense. For example, we
now have metrics-apm@settings and metrics-apm@mappings, which are
included by all APM metrics data streams.

We now set both default_pipeline and final_pipeline in the index
templates, preventing users from overriding them completely. The
default pipeline is always apm@default-pipeline, which performs
some rerouting of legacy data, and invokes user-defined @Custom
pipelines based on the data_stream.type and data_stream.dataset
fields. The final pipeline just performs built-in processing.

Certain index templates installed by Fleet are given
a priority of 150, so lower the priority to avoid
conflicts.

See https://github.com/elastic/kibana/blob/a18c68f7ac0b2cb6a46552328e9c6fc28c223970/x-pack/plugins/fleet/server/services/epm/elasticsearch/template/template.ts#L58

…eams

This goes closer to the Fleet-installed template priorities,
allowing for more builtin templates to be introduced without
affecting APM.

…eams

Because there's already an "apm" plugin,
we haven't yet solved all issues with rollovers,
and the templates need some more love.