[Java] add missing optional tensor list functions (#6640)

Update

[ghstack-poisoned]

Author: davidlin54

extension/android/src/main/java/org/pytorch/executorch/EValue.java

@@ -61,7 +61,7 @@ public class EValue {
     "ListInt",
     "ListTensor",
     "ListScalar",
-    "ListOptionalScalar",
+    "ListOptionalTensor",
   };
 
   @DoNotStrip private final int mTypeCode;
@@ -267,6 +267,12 @@ public Tensor[] toTensorList() {
     return (Tensor[]) mData;
   }
 
+  @DoNotStrip
+  public Optional<Tensor>[] toOptionalTensorList() {
+    preconditionType(TYPE_CODE_LIST_OPTIONAL_TENSOR, mTypeCode);
+    return (Optional<Tensor>[]) mData;
+  }
+
   private void preconditionType(int typeCodeExpected, int typeCode) {
     if (typeCode != typeCodeExpected) {
       throw new IllegalStateException(