Clean up event testing functions

[DimitrisJim]

Mostly in reference to the following chain of comments: #5475 (review)

AssertEvents seems to currently be used in only one place (event testing for 29-fee). Elsewhere we're currently using AssertEventsLegacy. These should be consolidated and cleaned up, there should ideally be one way to check for event emission.

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[crodriguezvega]

I propose we use AssertEvents and remove AssertEventsLegacy (which has the added benefit of removing the complicated EventsMap type alias). AssertEvents also supports asserting an slice of events where multiple events are of the same type.

[vishal-kanna]

@crodriguezvega Can i work on it?

[crodriguezvega]

Hi @vishal-kanna, yes, thank you! Please branch off from main to avoid weird diffs in the PR. :)

[akaladarshi]

Hey @crodriguezvega, is this task still open?

[crodriguezvega]

@akaladarshi Yes, I think this is still open, so would be great if you pick it up. I will assign it to you.