feat(core): add event service

[aaronc]

Description

Closes: #14685

This adds an event servicec type to the core module API which supports both ADR 032 typed events and legacy ABCI events.

It specifies which event methods should be assumed to be part of blockchain consensus and which ones should be assumed to be non-deterministic. Currently we don't support events as part of consensus, but this API attempts to lay the groundwork for adding them in the future and for also allowing other parts of the state machine to listen to such events.

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[alexanderbez]

LGTM, but how does this facilitate listening?

[aaronc]

LGTM, but how does this facilitate listening?

I removed the listener API from this PR so that that's a separate discussion

[amaury1093]

LGTM, pending some godoc clarification