Dexopt service-connectivity.

`service-connectivity` is a jar that system_server loads dynamically.
Such jars can be dexopted now. This CL adds `service-connectivity` to a
`systemserverclasspath_fragment`, which does not actually add the jar to
the classpath, but tells the build system to dexopt it.

NOTE: The corresponding `exported_systemserverclasspath_fragments` needs
to be added to the `prebuilt_apex` once a new prebuilt is dropped.

Bug: 203198541
Test: m com.android.tethering
Change-Id: I53745baaf1bc7142cc12a1e6cd8d84c9b338ac9d
Merged-In: I53745baaf1bc7142cc12a1e6cd8d84c9b338ac9d
(cherry picked from commit 9ecc66ddbaa0f85ad58b5d85ee2332fcddb0275f)
diff --git a/Tethering/Android.bp b/Tethering/Android.bp
index 1f9ef08..041a3ae 100644
--- a/Tethering/Android.bp
+++ b/Tethering/Android.bp
@@ -208,4 +208,5 @@
 sdk {
     name: "tethering-module-sdk",
     bootclasspath_fragments: ["com.android.tethering-bootclasspath-fragment"],
+    systemserverclasspath_fragments: ["com.android.tethering-systemserverclasspath-fragment"],
 }