Adjust Android package versioning to .NET 6

With .NET 6, the way Xamarin package versioning works has changed.

- The `ApplicationVersion` MSBuild property aims to replace
  `android:versionCode` in the manifest.
- The `ApplicationDisplayVersion` MSBuild property aims to replace
  `android:versionName` in the manifest.

More about this can be read in Xamarin docs:

    ec712da8c1/Documentation/guides/OneDotNetSingleProject.md

To this end:

- Manual `version{Code,Name}` specs are removed from
  `AndroidManifest.xml`, as they were preventing MSBuild properties
  from functioning properly.
- `Version` now defaults to 0.0.0, so that local builds don't appear
  like they were deployed (see `OsuGameBase.IsDeployedBuild`).
- `ApplicationDisplayVersion` now defaults to `Version`.
  This addresses the Android portion of #21498.
- `ApplicationVersion` can now be specified by command line,
  but still needs to be supplied manually for version detection to
  work correctly. See `OsuGameAndroid.AssemblyVersion` for more info.

Putting the pieces together, the complete publish command to deploy
a new build should look something like so:

    dotnet publish -f net6.0-android \
                   -r android-arm64 \
                   -c Release \
                   -p:Version=2022.1228.0 \
                   -p:ApplicationVersion=202212280

osu.Android/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" package="sh.ppy.osulazer" android:installLocation="auto" android:versionName="0.1.0">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="sh.ppy.osulazer" android:installLocation="auto">
 	<uses-sdk android:minSdkVersion="21" android:targetSdkVersion="31" />
 	<application android:allowBackup="true" android:supportsRtl="true" android:label="osu!" android:icon="@drawable/lazer" />
 </manifest>

osu.Android/osu.Android.csproj

@@ -8,6 +8,9 @@
     <UseMauiEssentials>true</UseMauiEssentials>
     <!-- This currently causes random lockups during gameplay. https://github.com/mono/mono/issues/18973 -->
     <EnableLLVM>false</EnableLLVM>
+    <Version>0.0.0</Version>
+    <ApplicationVersion Condition=" '$(ApplicationVersion)' == '' ">1</ApplicationVersion>
+    <ApplicationDisplayVersion Condition=" '$(ApplicationDisplayVersion)' == '' ">$(Version)</ApplicationDisplayVersion>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\osu.Game.Rulesets.Catch\osu.Game.Rulesets.Catch.csproj" />