all: add (*testing.B).ReportAllocs() to every benchmark

This ensures that we can properly track and catch allocation
slippages that could otherwise have been missed.

Fixes #2748

tstime/mono/mono_test.go

@@ -35,12 +35,14 @@ func TestUnmarshalZero(t *testing.T) {
 }
 
 func BenchmarkMonoNow(b *testing.B) {
+	b.ReportAllocs()
 	for i := 0; i < b.N; i++ {
 		Now()
 	}
 }
 
 func BenchmarkTimeNow(b *testing.B) {
+	b.ReportAllocs()
 	for i := 0; i < b.N; i++ {
 		time.Now()
 	}