Cache EventEmitter instances based on event names

[GeorgeTG]

To fix oni #2323
Should only be merged if oni #2355 is merged.
This change will brake oni without that PR (will also break all previous versions, maybe some version restrictions should be applied on both).

[akinsho]

@GeorgeTG thanks for the PR looks good to me, although we will need @bryphe to take a look as a change here will require the package version to be bumped and published to npm to use in oni-core