logtail: add instance metadata to the entry logtail

Allows instances that are running with the same machine ID (due to
cloning) to be distinguished.

Also adds sequence numbers to detect duplicates.

For tailscale/corp#5244

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

logpolicy/logpolicy.go

@@ -519,6 +519,8 @@ func New(collection string) *Policy {
 	}
 	if collection == logtail.CollectionNode {
 		c.MetricsDelta = clientmetric.EncodeLogTailMetricsDelta
+		c.IncludeProcID = true
+		c.IncludeProcSequence = true
 	}
 
 	if val := getLogTarget(); val != "" {