gradle: generate locales for per-app picking

Enable the per-app locale picking menu by adding the right metadata
automatically to the manifest with new AGP automation.

This attempts to follow:
https://developer.android.com/guide/topics/resources/app-languages#use-localeconfig

Using the new AGP feature:
https://developer.android.com/studio/preview/features#automatic-per-app-languages

It appears to work, and it also should squelch the "W AppCompatDelegate:
Checking for metadata for AppLocalesMetadataHolderService : " warnings
on old Android that syphyr pointed out.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui/build.gradle.kts

@@ -54,6 +54,9 @@ android {
             matchingFallbacks += "release"
         }
     }
+    androidResources {
+        generateLocaleConfig = true
+    }
     lint {
         disable += "LongLogTag"
         warning += "MissingTranslation"

ui/src/main/res/resources.properties

@@ -0,0 +1 @@
+unqualifiedResLocale=en-US