CtsMimeMapTestCases: Run in presubmit for relevant packages.

libcore.net.MimeMap might move to a different package in
future, in which case that part of its TEST_MAPPING would
move elsewhere.

Test: croot frameworks/base/mime && atest
Test: croot libcore/luni/src/main/java/libcore/net && atest
Bug: 136256059
Change-Id: Id4aa29e6bbda439009bf82376865bff5cf36a6d9

mime/TEST_MAPPING

+{
+  "presubmit": [
+    {
+      "name": "CtsMimeMapTestCases"
+    }
+  ]
+}