16k: Sign the APKs to support 4k/16k page sizes

The page agnostic targets have to support 4k/16k page sizes. For
these targets, the APKs have to be aligned at 16k boundaries.

Bug: 302343940
Test: source build/envsetup.sh
      lunch aosp_cf_arm64_phone_pgagnostic
      m
      launch_cvd -userdata_format=ext4
Change-Id: Ia0e39a90c0d6a3e62d450157fdfd5e3ee36d346e

tools/signapk/src/com/android/signapk/SignApk.java

@@ -687,7 +687,7 @@ class SignApk {
         if (entryName.endsWith(".so")) {
             // Align .so contents to memory page boundary to enable memory-mapped
             // execution.
-            return 4096;
+            return 16384;
         } else {
             return defaultAlignment;
         }