Allow reallocating when we use external arena.

Internal arena do not need reallocate as it is consecutive memory

Juliet/include/Core/Container/Vector.h

@@ -12,6 +12,7 @@ namespace Juliet
         void Create()
         {
             Assert(!Arena);
+            static_assert(AllowRealloc == false);
 
             DataFirst = DataLast = nullptr;
             Count                = 0;
@@ -25,7 +26,6 @@ namespace Juliet
         void Create(NonNullPtr<Arena> arena)
         {
             Assert(!Arena);
-            static_assert(AllowRealloc == false);
 
             DataFirst = DataLast = nullptr;
             Count                = 0;
@@ -72,6 +72,12 @@ namespace Juliet
         {
             Assert(Arena);
 
+            if (Count + 1 == Capacity)
+            {
+                Assert(AllowRealloc);
+                Reserve(Capacity * 2);
+            }
+
             Type* entry = Data + Count;
             *entry      = value;
 
@@ -87,6 +93,12 @@ namespace Juliet
         {
             Assert(Arena);
 
+            if (Count + 1 == Capacity)
+            {
+                Assert(AllowRealloc);
+                Reserve(Capacity * 2);
+            }
+
             Type* entry = Data + Count;
             *entry      = std::move(value);