Add CUJ tests

Add a cuj_tests binary that runs through a sequence of critical
user journey builds and collects metrics.

Bug: 145688720
Test: cuj_tests
Change-Id: I6bb1a3fc4a458fd8cea7b7c924f565d0cf3e6df3

ui/metrics/metrics_proto/metrics.proto

@@ -125,3 +125,16 @@ message ModuleTypeInfo {
   // The number of logical modules.
   optional uint32 num_of_modules = 3;
 }
+
+message CriticalUserJourneyMetrics {
+  // The name of a critical user journey test.
+  optional string name = 1;
+
+  // The metrics produced when running the critical user journey test.
+  optional MetricsBase metrics = 2;
+}
+
+message CriticalUserJourneysMetrics {
+  // A set of metrics from a run of the critical user journey tests.
+  repeated CriticalUserJourneyMetrics cujs = 1;
+}