Verify the existence of debug symbols in gradle_plugin_bundle_test (#162645)

A small piece of flutter/flutter#162464 that I
wanted to land anyways.

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Co-authored-by: Gray Mackall <[email protected]>

Author: gmackall

dev/devicelab/bin/tasks/gradle_plugin_bundle_test.dart

@@ -39,6 +39,8 @@ Future<void> main() async {
           'base/lib/arm64-v8a/libflutter.so',
           'base/lib/armeabi-v7a/libapp.so',
           'base/lib/armeabi-v7a/libflutter.so',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/arm64-v8a/libflutter.so.sym',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/armeabi-v7a/libflutter.so.sym',
         ], await getFilesInAppBundle(releaseBundle));
       });
 
@@ -72,6 +74,8 @@ Future<void> main() async {
           'base/lib/arm64-v8a/libflutter.so',
           'base/lib/armeabi-v7a/libapp.so',
           'base/lib/armeabi-v7a/libflutter.so',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/arm64-v8a/libflutter.so.sym',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/armeabi-v7a/libflutter.so.sym',
         ], await getFilesInAppBundle(bundleFromGradlePath));
 
         section('Build app bundle using the flutter tool - flavor: flavor_underscore');
@@ -103,6 +107,8 @@ Future<void> main() async {
           'base/lib/arm64-v8a/libflutter.so',
           'base/lib/armeabi-v7a/libapp.so',
           'base/lib/armeabi-v7a/libflutter.so',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/arm64-v8a/libflutter.so.sym',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/armeabi-v7a/libflutter.so.sym',
         ], await getFilesInAppBundle(flavorUnderscoreBundlePath));
 
         section('Build app bundle using the flutter tool - flavor: production');
@@ -134,6 +140,8 @@ Future<void> main() async {
           'base/lib/arm64-v8a/libflutter.so',
           'base/lib/armeabi-v7a/libapp.so',
           'base/lib/armeabi-v7a/libflutter.so',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/arm64-v8a/libflutter.so.sym',
+          'BUNDLE-METADATA/com.android.tools.build.debugsymbols/armeabi-v7a/libflutter.so.sym',
         ], await getFilesInAppBundle(productionBundlePath));
       });