Bump to r8 3.0.73 (#6620)

Context: https://r8.googlesource.com/r8/+/refs/tags/3.0.73
Context: https://mvnrepository.com/artifact/com.android.tools/r8/3.0.73

Bump from r8 2.2.64 to 3.0.73.

* [tests] update MultiDexR8ConfigWithNoCodeShrinking

78dd021 introduced the `MultiDexR8ConfigWithNoCodeShrinking(false)`
test that asserts we get the warning:

    R8 : warning : Missing class: java.lang.ClassValue

The latest version of r8 no longer emits this warning, so Google must
have *fixed* something here.

The test still seems useful to build a multi-dex application with a
`@(ProguardConfiguration)` item, so let's drop one test case and just
assert that the warning isn't there. The test is no longer
parameterized.

Documentation/release-notes/r8-3.0.73.md

@@ -0,0 +1,4 @@
+### D8/R8 version update to 3.0.73
+
+The version of the [D8 dexer and R8 shrinker](https://r8.googlesource.com/r8)
+included in Xamarin.Android has been updated from 2.2.64 to 3.0.73.

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs

@@ -1317,7 +1317,7 @@ public void MultiDexAndCodeShrinker ([Values ("proguard", "r8")] string linkTool
 		}
 
 		[Test]
-		public void MultiDexR8ConfigWithNoCodeShrinking ([Values (true, false)] bool useConfig)
+		public void MultiDexR8ConfigWithNoCodeShrinking ()
 		{
 			var proj = new XamarinAndroidApplicationProject () {
 				IsRelease = true,
@@ -1349,20 +1349,15 @@ abstract class ExtendsClassValue extends ClassValue<Boolean> {}
 klGRVNULk1GUEsBAhQAFAAICAgAHHONUB4E1g/HAAAAEgEAABcAAAAAAAAAAAAAAAAAugAAAEV4d
 GVuZHNDbGFzc1ZhbHVlLmNsYXNzUEsFBgAAAAADAAMAwgAAAMYBAAAAAA==
 				") });
-			if (useConfig)
-				proj.OtherBuildItems.Add (new BuildItem ("ProguardConfiguration", "proguard.cfg") {
-					TextContent = () => "-dontwarn java.lang.ClassValue"
-				});
+			proj.OtherBuildItems.Add (new BuildItem ("ProguardConfiguration", "proguard.cfg") {
+				TextContent = () => "-dontwarn java.lang.ClassValue"
+			});
 			using (var builder = CreateApkBuilder ()) {
 				Assert.True (builder.Build (proj), "Build should have succeeded.");
 				string warning = builder.LastBuildOutput
 						.SkipWhile (x => !x.StartsWith ("Build succeeded.", StringComparison.Ordinal))
 						.FirstOrDefault (x => x.Contains ("R8 : warning : Missing class: java.lang.ClassValue"));
-				if (useConfig) {
-					Assert.IsNull (warning, "Build should have completed without an R8 warning for `java.lang.ClassValue`.");
-					return;
-				}
-				Assert.IsNotNull (warning, "Build should have completed with an R8 warning for `java.lang.ClassValue`.");
+				Assert.IsNull (warning, "Build should have completed without an R8 warning for `java.lang.ClassValue`.");
 			}
 		}
 

src/r8/build.gradle

@@ -15,7 +15,7 @@ repositories {
 }
 
 dependencies {
-    compile group: 'com.android.tools', name: 'r8', version: '2.2.64'
+    compile group: 'com.android.tools', name: 'r8', version: '3.0.73'
 }
 
 jar {