Context: https://github.com/google/bundletool/releases/tag/1.15.1
Changes: google/bundletool@1.8.1...1.15.1

We are seeing an error with API 34:

    XABBA7024: Xamarin.Tools.Zip.ZipIOException: The file 'obj\Release\android\bin\base.zip' is not a ZIP archive.

We wonder if updating `bundletool` will help. It was last updated in
989dc07.

Context: https://github.com/xamarin/xamarin-android/blob/f1d59181c8daaa8d2abcdfd151b592ece49155ca/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/ManifestTest.cs#L650-L651

The `ModifyManifest` test actually writes "too much" to the
`AndroidManifest.xml` file, removing the `<application>` element,
causing the latest version of `bundletool` to error with:

    BT One element <application> was expected, but none were found.

To solve this, let's just set `application:versionCode` in the test
instead.

This reverts commit 43fe871.

Work around an MSBuild issue:

    error MSB4012: The expression "@(_XmlNodes->'%(Identity)', ' ')@(_Permissions)" cannot be used in this context. Item lists cannot be concatenated with other strings where an item list is expected. Use a semicolon to separate multiple item lists.