Add extra regression test for generic record.

Author: yilinwei

tests/pos-java16+/java-records-patmatch/FromScala.scala

@@ -23,3 +23,9 @@ object C:
     r match {
       case R1(i, _) => i
     }
+
+  def useR2: String =
+    val r = R2("asd")
+    r match {
+      case R2(s) => s
+    }

tests/pos-java16+/java-records-patmatch/R2.java

@@ -0,0 +1 @@
+public record R2<T>(T t) {}