coroutines: use lifecycleScope where appropriate

There's still a bit of GlobalScope lingering around, which might be
removable.

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

ui/src/main/java/com/wireguard/android/util/Extensions.kt

@@ -9,6 +9,10 @@ import android.content.Context
 import android.util.TypedValue
 import androidx.annotation.AttrRes
 import androidx.fragment.app.Fragment
+import androidx.lifecycle.lifecycleScope
+import androidx.preference.Preference
+import com.wireguard.android.activity.SettingsActivity
+import kotlinx.coroutines.CoroutineScope
 
 fun Context.resolveAttribute(@AttrRes attrRes: Int): Int {
     val typedValue = TypedValue()
@@ -19,3 +23,9 @@ fun Context.resolveAttribute(@AttrRes attrRes: Int): Int {
 fun Fragment.requireTargetFragment(): Fragment {
     return requireNotNull(targetFragment) { "A target fragment should always be set for $this" }
 }
+
+val Preference.activity: SettingsActivity
+    get() = if (this.context is SettingsActivity) this.context as SettingsActivity else throw IllegalStateException("Failed to resolve SettingsActivity")
+
+val Preference.lifecycleScope: CoroutineScope
+    get() = this.activity.lifecycleScope