Add TEST_MAPPING to system/timezone.

To run the APEX tests (including timezone_data_e2e_tests) at presubmit
time.

Bug: 129996626
Test: run atest locally
Change-Id: I256092636cfc51b5d319d8293a4bb81eaee61865
diff --git a/TEST_MAPPING b/TEST_MAPPING
new file mode 100644
index 0000000..a2e98cc
--- /dev/null
+++ b/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "imports": [
+    {
+      "path": "system/apex/tests"
+    }
+  ]
+}