8289570: SegmentAllocator:allocateUtf8String(String str) default behavior mismatch to spec

Reviewed-by: alanb, psandoz

src/java.base/share/classes/jdk/internal/foreign/Utils.java

@@ -146,7 +146,7 @@ public final class Utils {
     }
 
     public static MemorySegment toCString(byte[] bytes, SegmentAllocator allocator) {
-        MemorySegment addr = allocator.allocate(bytes.length + 1, 1L);
+        MemorySegment addr = allocator.allocate(bytes.length + 1);
         copy(addr, bytes);
         return addr;
     }

test/jdk/java/foreign/TestSegmentAllocators.java

@@ -185,6 +185,25 @@ public class TestSegmentAllocators {
         assertEquals(calls.get(), 7);
     }
 
+    @Test
+    public void testStringAllocateDelegation() {
+        AtomicInteger calls = new AtomicInteger();
+        SegmentAllocator allocator = new SegmentAllocator() {
+            @Override
+            public MemorySegment allocate(long bytesSize, long bytesAlignment) {
+                return MemorySegment.allocateNative(bytesSize, bytesAlignment, MemorySession.openImplicit());
+            }
+
+            @Override
+            public MemorySegment allocate(long size) {
+                calls.incrementAndGet();
+                return allocate(size, 1);
+            };
+        };
+        allocator.allocateUtf8String("Hello");
+        assertEquals(calls.get(), 1);
+    }
+
 
     @Test(dataProvider = "arrayAllocations")
     public <Z> void testArray(AllocationFactory allocationFactory, ValueLayout layout, AllocationFunction<Object, ValueLayout> allocationFunction, ToArrayHelper<Z> arrayHelper) {