[ResponseOps] space-agnostic admin-only route to return all rules / connectors

[pmuellr]

For support purposes, and specifically the Kibana diagnostics tool, we're considering adding routes for rules and connectors that would return all the relevant SO's like their find routes currently do, except it would return ALL the rules / connectors across all spaces, and presumably require "superuser" access, or equivalent sort of authorization gating.

This would greatly simplify the ability for users to pull all the alerting rules / connectors in a much smaller set of requests. The alternative is:

• find all spaces (may require pagination)
• for each space:
  • find all rules in this space (may require pagination)
  • find all connectors in this space (may require pagination)

This would change to:

• find all rules (may require pagination)
• find all connectors (may require pagination)

I don't believe we actually return the space in the rules or connectors, and we'd need to do that for this call, so we'd need to figure out how to do that. For instance:

• add a new field to the returned output data for rules / connectors indicating the spaces
• return the spaces as top-level keys of the response, with the value being an array of the data relevant to that space
• some even more complex data structure (more indirection; for example, an array of spaces, array of rule/connectors, final array of pairs of those indices)

The first sounds better - the data shape is easier to deal with, and will be less confusing when we support rules / connectors in multiple spaces (in the second form, presumably objects in multiple spaces would be duplicated under each space key).

Note: I don't think we have an issue open for this, and did a cursory search and didn't find one. But if we do, we can close this as a DUP

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)

[pmuellr]

During a backlog grooming session, we decided to close this issue in favor of the new capability of Allowing users to see event logs from all spaces they have access to, implemented in #140449

At least for the non-diagnostic tool purposes (mentioned in the top comment), we think this should handle the needs users will have for cross-space visibility of alerting status.