Create helper functions for publishing of packet sent and acknowledgement sent events

[crodriguezvega]

Summary

We currently have some helper functions for publishing events on packet received, packet acknowledged and packet timed out.

https://github.com/cosmos/ibc-go/blob/main/modules/core/04-channel/keeper/events.go

We also emit events for packet sent (here) and acknowledgement sent (here), but those do not have a helper function.

The proposal is to create helper functions for these two events as well. The rationale is to make both packet event emitting code and the code of the functions using it more similar.

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