Add missing mkLastIndexOf method and CharSort case to Java API (#8002)

* Initial plan

* Add mkLastIndexOf method and CharSort support to Java API

- Added mkLastIndexOf method to Context.java for extracting last index of sub-string
- Added Z3_CHAR_SORT case to Sort.java's create() method switch statement
- Added test file to verify both fixes work correctly

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Fix author field in test file

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Delete examples/java/TestJavaAPICompleteness.java

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
Co-authored-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/api/java/Context.java

@@ -2226,6 +2226,15 @@ public class Context implements AutoCloseable {
         return (IntExpr)Expr.create(this, Native.mkSeqIndex(nCtx(), s.getNativeObject(), substr.getNativeObject(), offset.getNativeObject()));
     }
 
+    /**
+     * Extract the last index of sub-string.
+     */
+    public final <R extends Sort> IntExpr mkLastIndexOf(Expr<SeqSort<R>> s, Expr<SeqSort<R>> substr)
+    {
+        checkContextMatch(s, substr);
+        return (IntExpr)Expr.create(this, Native.mkSeqLastIndex(nCtx(), s.getNativeObject(), substr.getNativeObject()));
+    }
+
     /**
      * Replace the first occurrence of src by dst in s.
      */

src/api/java/Sort.java

@@ -144,6 +144,8 @@ public class Sort extends AST
             return new SeqSort<>(ctx, obj);
         case Z3_RE_SORT:
             return new ReSort<>(ctx, obj);
+        case Z3_CHAR_SORT:
+            return new CharSort(ctx, obj);
         default:
             throw new Z3Exception("Unknown sort kind");
         }