Generate a default wrapper for device java_binary

Any device java_binary that doesn't have a specific wrapper must
have a main_class property, which is used to generate its default
wrapper. Otherwise its build should fail.

Bug: 250851599
Test: TestDeviceBinaryWrapperGeneration in java_test.go
Change-Id: Ice4c580bcfc1b92f95e217b39e984c55d25a3a02
diff --git a/java/dexpreopt_test.go b/java/dexpreopt_test.go
index 1c1070a..3d2c5c3 100644
--- a/java/dexpreopt_test.go
+++ b/java/dexpreopt_test.go
@@ -63,6 +63,7 @@
 				java_binary {
 					name: "foo",
 					srcs: ["a.java"],
+					main_class: "foo.bar.jb",
 				}`,
 			enabled: true,
 		},