Improve EntityEvent fields

[mlange-42]

• Pass events by value/copy instead of by pointer. It torned out heap escape is much more expensive than copying.
• Removes event fields that are accessible from the world.
• Adds event fields to better identify relation changes.
• Reduces the size of EntityEvent by 30%.

[coveralls]

Pull Request Test Coverage Report for Build 7533551176

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 7528343499:	0.0%
Covered Lines:	4989
Relevant Lines:	4989

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💛 - Coveralls