Add more enums for the client and process attributes of SystemApi

For the client attribute, we have
- MODULE_APPS for representing APKs implementing modules which are
considered part of the platform
- MODULE_LIBRARIES for representing jars inside modules.

For the process attribute, we have
- SYSTEM_SERVER for representing the system_server process.

For example, @SystemApi(client=MODULE_LIBRARIES,process=ALL) actually
means that the API is meant to be available for classes in the
bootclasspath but not to the classes from the app classloader.

Bug: 140202860
Test: m
Change-Id: Iba6a564a0967e4d109164849ee6d6500d46469de
diff --git a/services/Android.bp b/services/Android.bp
index 8376d2b..3248e3d 100644
--- a/services/Android.bp
+++ b/services/Android.bp
@@ -111,7 +111,7 @@
     srcs: [":services-sources"],
     installable: false,
     // TODO: remove the --hide options below
-    args: " --show-single-annotation android.annotation.SystemApi\\(client=android.annotation.SystemApi.Client.INTERNAL,process=android.annotation.SystemApi.Process.SYSTEM_SERVER\\)" +
+    args: " --show-single-annotation android.annotation.SystemApi\\(client=android.annotation.SystemApi.Client.MODULE_LIBRARIES,process=android.annotation.SystemApi.Process.SYSTEM_SERVER\\)" +
         " --hide-annotation android.annotation.Hide" +
         " --hide-package com.google.android.startop.iorap" +
         " --hide ReferencesHidden" +