Bug 1480854 - Use classic icons again on platforms prior to Oreo. r=jchen

We want to use the classic, non-adaptive icon again as our launcher icon on
Android versions prior to Oreo, as well as to continue using it in various
places within our app.

Unfortunately this means that we still have to provide duplicate resources for
those two purposes:
Because we don't want to use the adaptive icon internally, we can't use the same
resource directly for both internal usage and our launcher icon, because other-
wise on Oreo and above we'd receive the adaptive icon that way.
One possible workaround would have been to use the PNG files of our classic icon
directly as a drawable for internal useage and then create a differently named
XML bitmap for our launcher icon, which in turn would be overridden by the
adaptive icon on Oreo and above.
Unfortunately, modern usage demands that the launcher icon should be provided as
a mipmap resource, where XML bitmaps
- aren't officially supported
- unofficially work with some devices/launchers, but not all.

Therefore, our only choice is to provide separate drawables for our internal
icon and our launcher icon, even if prior to Android O both will have the same
contents. We'll also get rid of the separate round icon again, since
- on Android O and above, both round and non-round icons were using the same
  adaptive icon anyway
- prior to Android O our normal icon is already round enough, but not round
  enough to pass the lint check

--HG--
extra : rebase_source : 6c06c903f4fed2ef4aee3c5a915e18c437c5b510
extra : amend_source : ab3eab8e4dc2523a336aef2a4d2889ab7dbc76b9
extra : intermediate-source : 56f9803240157892066fa5b1703b8fe50c28020d
extra : source : 6183adcbfc9d81ab0cb854a4734a98f10a897d6b

mobile/android/base/AndroidManifest.xml.in

@@ -25,7 +25,6 @@
 
     <application android:label="@string/moz_app_displayname"
                  android:icon="@mipmap/ic_launcher"
-                 android:roundIcon="@mipmap/ic_launcher_round"
                  android:logo="@drawable/logo"
                  android:name="@MOZ_ANDROID_APPLICATION_CLASS@"
                  android:hardwareAccelerated="true"

mobile/android/branding/beta/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@color/ic_launcher_background"/>
-    <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
-</adaptive-icon>

mobile/android/branding/nightly/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@color/ic_launcher_background"/>
-    <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
-</adaptive-icon>

mobile/android/branding/official/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@color/ic_launcher_background"/>
-    <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
-</adaptive-icon>

mobile/android/branding/unofficial/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@color/ic_launcher_background"/>
-    <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
-</adaptive-icon>