Address additional PR feedback

Signed-off-by: Jeremy Ong <jcong@amazon.com>

Code/Framework/AzCore/AzCore/Debug/Budget.h

@@ -73,7 +73,7 @@ namespace AZ::Debug
 
 // If using a budget defined in a different C++ source file, add AZ_DECLARE_BUDGET(yourBudget); somewhere in your source file at namespace
 // scope Alternatively, AZ_DECLARE_BUDGET can be used in a header to declare the budget for use across any users of the header
-#define AZ_DECLARE_BUDGET(name) extern ::AZ::Debug::Budget* AZ_BUDGET_GETTER(name)()
+#define AZ_DECLARE_BUDGET(name) ::AZ::Debug::Budget* AZ_BUDGET_GETTER(name)()
 
 // Declare budgets that are core engine budgets, or may be shared/needed across multiple external gems
 // You should NOT need to declare user-space or budgets with isolated usage here. Prefer declaring them local to the module(s) that use

Code/Framework/AzCore/AzCore/Debug/BudgetTracker.cpp

@@ -19,7 +19,7 @@ namespace AZ::Debug
 {
     constexpr static const char* BudgetTrackerEnvName = "budgetTrackerEnv";
 
-    struct BudgetTrackerImpl
+    struct BudgetTracker::BudgetTrackerImpl
     {
         AZStd::unordered_map<const char*, Budget> m_budgets;
     };
@@ -65,11 +65,7 @@ namespace AZ::Debug
     {
         AZStd::scoped_lock lock{ m_mutex };
 
-        auto it = m_impl->m_budgets.find(budgetName);
-        if (it == m_impl->m_budgets.end())
-        {
-            it = m_impl->m_budgets.try_emplace(budgetName, budgetName, crc).first;
-        }
+        auto it = m_impl->m_budgets.try_emplace(budgetName, budgetName, crc).first;
 
         return it->second;
     }

Code/Framework/AzCore/AzCore/Debug/BudgetTracker.h

@@ -31,11 +31,13 @@ namespace AZ::Debug
         Budget& GetBudget(const char* budgetName, uint32_t crc);
 
     private:
+        struct BudgetTrackerImpl;
+
         AZStd::mutex m_mutex;
 
         // The BudgetTracker is likely included in proportionally high number of files throughout the
         // engine, so indirection is used here to avoid imposing excessive recompilation in periods
         // while the budget system is iterated on.
-        struct BudgetTrackerImpl* m_impl = nullptr;
+        BudgetTrackerImpl* m_impl = nullptr;
     };
 } // namespace AZ::Debug