feat(app,android): a new icon, and a launcher label that fits

The icon follows proton-drive-linux's logo: a violet gradient tile with
a darker lower edge, and a white play mark with a soft shadow, cut into
the blocks a revision is fetched in. The SVG, the window PNG and the
Windows .ico are rendered from one source.

On Android it is an adaptive icon with a monochrome layer for themed
icons, and the notification glyph is the same mark. The app is named
"Proton Stream"; the launcher shows "Stream", since "proton-stream" was
cut to "proton-st…".

android/app/src/main/AndroidManifest.xml

@@ -11,7 +11,7 @@
         android:name=".ProtonStreamApplication"
         android:allowBackup="false"
         android:dataExtractionRules="@xml/data_extraction_rules"
-        android:icon="@drawable/ic_launcher_foreground"
+        android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:supportsRtl="true"
         android:theme="@style/Theme.ProtonStream">
@@ -29,6 +29,7 @@
 
         <activity
             android:name=".MainActivity"
+            android:label="@string/launcher_name"
             android:configChanges="screenSize|smallestScreenSize|screenLayout|orientation|uiMode|density|fontScale|locale|layoutDirection|keyboardHidden"
             android:exported="true"
             android:launchMode="singleTask"