[ResponseOps][Rules] Create @kbn-response-ops/rule_params_constants package

[adcoelho]

Summary

To follow up on our work migrating the different rule type parameters to a separate package, we need to identify any constants that have been duplicated and move them to a separate @kbn-response-ops/rule_params_constants package.

This will allow the constants to be imported directly from this new package(and eliminate duplication).

The constants could not be imported directly from rule_params since it uses @kbn/config-schema which is not supported in the frontend.

One example is the Aggregators enum introduced in this PR.

[elasticmachine]

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