[Event log] Update public API routes to resolve SO ids

[chrisronline]

As part of the research done in #100666, we need to update the the following two routes to properly resolve saved object ids:

• https://github.com/elastic/kibana/blob/master/x-pack/plugins/event_log/server/routes/find_by_ids.ts#L55
• https://github.com/elastic/kibana/blob/master/x-pack/plugins/event_log/server/routes/find.ts#L49

In order to properly resolve the saved object id, we will need access to the current space which can either be determined and passed down from the route, or resolved later in the function chain.

One slight complication here is using the appropriate space for saved object id resolution, as the caller's space might differ from the namespace defined in the event log itself.

I don't expect this part of the code to need to worry about how to handle possible responses from the .resolve() API, but rather just use it to ensure we fetch the correct saved object.

For reference, here is a PoC commit (part of the overall PoC) of how we might do this.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[chrisronline]

I'm going to close this out, as the original research is invalid and need to be reworked. If this item is still applicable, we still reopen this ticket.