Update traces duration mappings with appropriate unit type

Author: Bluefinger

x-pack/plugin/apm-data/src/main/resources/component-templates/[email protected]

@@ -43,6 +43,8 @@ template:
       # span.*
       span.duration.us:
         type: long
+        meta:
+          unit: micros
       span.representative_count:
         type: scaled_float
         scaling_factor: 1000
@@ -57,6 +59,8 @@ template:
         dynamic: false
       transaction.duration.us:
         type: long
+        meta:
+          unit: micros
       transaction.representative_count:
         type: scaled_float
         scaling_factor: 1000