ref: move decl/impl from SentryEvent (MetricKit) to SenryEvent .h/.m … #4406

Job	Run time
Build UITests (macos-12, 13.4.1)	4m 28s
Build UITests (macos-13, 14.3)	5m 26s
Run UI Tests for iOS-16 on Sauce Labs	20m 41s
Run UI Tests for iOS-15 on Sauce Labs	12m 51s
Run UI Tests for iPhone-Pro on Sauce Labs	3m 51s
Run UI Tests for iOS-14 on Sauce Labs	20m 44s
Run UI Tests for iOS-13 on Sauce Labs	3m 40s
Run UI Tests for iOS-12 on Sauce Labs	13m 49s
	1h 25m 30s

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