Rename updatable-library to apex-library

Mostly for consistency with the names used in related changes.

Test: atest com.android.server.pm.parsing.library.ApexSharedLibraryUpdaterTest com.android.server.systemconfig.SystemConfigTest

Bug: 191978330
Change-Id: Ic4ccc0fdca100b576e28bc0918d378cabae9ce61

core/java/com/android/server/SystemConfig.java

@@ -849,8 +849,8 @@ public class SystemConfig {
                             XmlUtils.skipCurrentTag(parser);
                         }
                     } break;
-                    case "updatable-library":
-                        // "updatable-library" is meant to behave exactly like "library"
+                    case "apex-library":
+                        // "apex-library" is meant to behave exactly like "library"
                     case "library": {
                         if (allowLibs) {
                             String lname = parser.getAttributeValue(null, "name");

services/tests/servicestests/src/com/android/server/systemconfig/SystemConfigTest.java

@@ -357,13 +357,13 @@ public class SystemConfigTest {
 
     /**
      * Tests that readPermissions works correctly for a library using the new
-     * {@code updatable-library} tag.
+     * {@code apex-library} tag.
      */
     @Test
     public void readPermissions_allowLibs_parsesUpdatableLibrary() throws IOException {
         String contents =
                 "<permissions>\n"
-                        + "    <updatable-library \n"
+                        + "    <apex-library \n"
                         + "        name=\"foo\"\n"
                         + "        file=\"" + mFooJar + "\"\n"
                         + "        on-bootclasspath-before=\"10\"\n"