logs consistency

[michel-laterman]

fleet-server has log lines with inconsistent attributes.

For example:

fleet-server/internal/pkg/policy/policy_output.go

Line 54 in 5e8a1e9

Str("fleet.policy.output.name", p.Name).Logger()

fleet-server/internal/pkg/policy/self.go

Line 265 in 5e8a1e9

logger.Error().Err(err).Str("outputName", outputName).Msg(doc.Message)

Both refer to policy outputs but are named different things.
We should go through the codebase and try to make these more consistent (following ecs)

[juliaElastic]

Few more places to make consistent:
The action type is logged under different fields:

ack event
actionId

Action delivered to agent on checkin
id

Found that the policy id is also logged under different names:

New revision of policy received and added to the queue
fleet.policy.id

Policy coordinator added a new policy revision
policy_id

[juliaElastic]

Revision_idx fields are changed in this pr #3234

[juliaElastic]

Found one more place where revision and coordinator idx is logged under a different name:

fleet-server/internal/pkg/api/handleCheckin.go

Lines 768 to 769 in 6189520

	Int64("fleet.policyRevision", pp.Policy.RevisionIdx).
	Int64("fleet.policyCoordinator", pp.Policy.CoordinatorIdx).