Agree on API for agent event queries

Shroom has agentEconomicEvents(latestNumberOfDays: 30), which seems like an older API.

My vote currently goes to something like:

input agentEventSearchParams {
  searchString: String
  action: ID
  startDate: DateTime
  endDate: DateTime
}
interface Agent {
    economicEvents(filter: agentEventSearchParams, start: ID, limit: Int)
}

Also see this as a general format for graph search edges. This way, we can iteratively add filter criteria without upsetting existing code.

We would also need to define what searchString is supposed to match in all cases.