Use new applicationIdTextResource method in the gradle API.

[runningcode]

According to the release notes there is a new applicationIdTextResource method in the Gradle build API which returns the application ID of a variant. We can use this instead of the xml slurper in the butterknife gradle plugin here: https://github.com/JakeWharton/butterknife/blob/master/butterknife-gradle-plugin/src/main/java/butterknife/plugin/ButterKnifePlugin.kt#L45

https://androidstudio.googleblog.com/2018/06/android-studio-33-canary-1-available.html

We should probably wait until 3.3 is stable and released before doing this.