Include tags in trace data.

The tags item in the trace data is arbitrary metadata added to `build`
steps by Soong (and my Kati via `.KATI_TAGS` target-specific
variables). Include this in the perfetto trace so we can analyze it.

Bug: http://b/259130368
Test: End to end test tracing cp time in dist targets
Change-Id: I85d33f579dc40dbae616b24cd4cb150d86262470

ui/status/ninja.go

@@ -174,6 +174,7 @@ func (n *NinjaReader) run() {
 						IOOutputKB:                 msg.EdgeFinished.GetIoOutputKb(),
 						VoluntaryContextSwitches:   msg.EdgeFinished.GetVoluntaryContextSwitches(),
 						InvoluntaryContextSwitches: msg.EdgeFinished.GetInvoluntaryContextSwitches(),
+						Tags:                       msg.EdgeFinished.GetTags(),
 					},
 				})
 			}