[templates] use .NET logo on app icons (#7065)

Fixes: #7041

I got these image files by doing:

	dotnet new maui
	dotnet build -f net6.0-android

Then look in `obj\Debug\net6.0-android\resizetizer\r`.  The `maui`
template uses an `.svg` and generates these files at build time.
Since we don't have Resizetizer here, we can just add the build
output instead.

I used the exact filenames that dotnet/maui uses, I don't think we
were particular about the `ic_launcher` named used before?

![image](https://user-images.githubusercontent.com/840039/171743063-eaaba8aa-d72b-47e7-98f5-ce30e18ea5d0.png)

Author: jonathanpeppers

src/Microsoft.Android.Templates/android/AndroidManifest.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
-  <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true">
+  <application android:allowBackup="true" android:icon="@mipmap/appicon" android:label="@string/app_name" android:roundIcon="@mipmap/appicon_round" android:supportsRtl="true">
   </application>
   <uses-permission android:name="android.permission.INTERNET" />
 </manifest>

src/Microsoft.Android.Templates/android/Resources/mipmap-anydpi-v26/appicon.xml

@@ -0,0 +1,4 @@
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+  <background android:drawable="@mipmap/appicon_background" />
+  <foreground android:drawable="@mipmap/appicon_foreground" />
+</adaptive-icon>

src/Microsoft.Android.Templates/android/Resources/mipmap-anydpi-v26/appicon_round.xml

@@ -0,0 +1,4 @@
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+  <background android:drawable="@mipmap/appicon_background" />
+  <foreground android:drawable="@mipmap/appicon_foreground" />
+</adaptive-icon>