Make lots of tests run in parallel

Putting t.Parallel() in each test makes them run in parallel.
Additional t.Parallel() could be added to each subtest, although
that requires making a local copy of the loop variable for
table driven tests.

Test: m checkbuild
Change-Id: I5d9869ead441093f4d7c5757f2447385333a95a4
diff --git a/ui/metrics/time_test.go b/ui/metrics/time_test.go
index d73080a..16d6a20 100644
--- a/ui/metrics/time_test.go
+++ b/ui/metrics/time_test.go
@@ -22,6 +22,7 @@
 )
 
 func TestEnd(t *testing.T) {
+	t.Parallel()
 	startTime := time.Date(2020, time.July, 13, 13, 0, 0, 0, time.UTC)
 	dur := time.Nanosecond * 10
 	initialNow := _now