Require all audit events to be able to be trimmed (#46505)

* add TrimToMaxSize methods for all audit events and make it a required method

* ensure callers of TrimToMaxSize check the size of the returned event

---------

api/types/events/api.go

@@ -69,6 +69,14 @@ type AuditEvent interface {
 	GetClusterName() string
 	// SetClusterName sets the name of the teleport cluster on the event.
 	SetClusterName(string)
+
+	// TrimToMaxSize returns a copy of the event trimmed to a smaller
+	// size. The desired size may not be achievable so callers
+	// should always check the size of the returned event before
+	// using it. Generally fields that are unique to the event
+	// will be trimmed, other fields are not currently modified
+	// (ie *Metadata messages).
+	TrimToMaxSize(maxSizeBytes int) AuditEvent
 }
 
 // Emitter emits audit events.