tpl/collections: Add Merge benchmark

tpl/collections/merge_test.go

@@ -159,6 +159,18 @@ func TestMerge(t *testing.T) {
 	}
 }
 
+func BenchmarkMerge(b *testing.B) {
+	ns := newNs()
+
+	for i := 0; i < b.N; i++ {
+		ns.Merge(
+			map[string]any{"a": 42, "c": 3, "e": 11},
+			map[string]any{"a": 1, "b": 2},
+			map[string]any{"a": 9, "c": 4, "d": 7},
+		)
+	}
+}
+
 func TestMergeDataFormats(t *testing.T) {
 	c := qt.New(t)
 	ns := newNs()