[DEV-787] Dynamic value mapper for event metadata #81

Job	Run time
build / Build (11)	1m 13s
Tests (Previous LTS) / load_configuration / load	2s
build / Build (17)	1m 22s
build / Build (8)	1m 11s
Tests (Previous LTS) / Secure (Streams)	1m 40s
Tests (Previous LTS) / Secure (PersistentSubscriptions)	2m 12s
Tests (Previous LTS) / Single node (PersistentSubscriptions)	1m 47s
Tests (Previous LTS) / Single node (MultiStreamAppend)	1m 26s
Tests (Previous LTS) / Single node (Telemetry)	1m 31s
Tests (Previous LTS) / Single node (Streams)	1m 35s
Tests (Previous LTS) / Cluster (Streams)	1m 36s
Tests (Previous LTS) / Cluster (MultiStreamAppend)	1m 40s
Tests (Previous LTS) / Cluster (PersistentSubscriptions)	1m 44s
	18m 59s

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