AK: Use default constructor/destructor instead of declaring an empty one

Default implementations allow for more optimizations.
See: https://pvs-studio.com/en/docs/warnings/v832/

AK/CircularQueue.h

@@ -17,9 +17,7 @@ class CircularQueue {
     friend CircularDuplexStream<Capacity>;
 
 public:
-    CircularQueue()
-    {
-    }
+    CircularQueue() = default;
 
     ~CircularQueue()
     {

AK/DistinctNumeric.h

@@ -52,9 +52,7 @@ class DistinctNumeric {
     using Self = DistinctNumeric<T, X, Incr, Cmp, Bool, Flags, Shift, Arith>;
 
 public:
-    constexpr DistinctNumeric()
-    {
-    }
+    constexpr DistinctNumeric() = default;
 
     constexpr DistinctNumeric(T value)
         : m_value { value }

AK/FixedArray.h

@@ -15,7 +15,7 @@ namespace AK {
 template<typename T>
 class FixedArray {
 public:
-    FixedArray() { }
+    FixedArray() = default;
     explicit FixedArray(size_t size)
         : m_size(size)
     {

AK/NonnullPtrVector.h

@@ -16,9 +16,7 @@ class NonnullPtrVector : public Vector<PtrType, inline_capacity> {
     using Base = Vector<PtrType, inline_capacity>;
 
 public:
-    NonnullPtrVector()
-    {
-    }
+    NonnullPtrVector() = default;
 
     NonnullPtrVector(Vector<PtrType>&& other)
         : Base(static_cast<Base&&>(other))

AK/RedBlackTree.h

@@ -46,7 +46,7 @@ public:
 
 protected:
     BaseRedBlackTree() = default; // These are protected to ensure no one instantiates the leaky base red black tree directly
-    virtual ~BaseRedBlackTree() {};
+    virtual ~BaseRedBlackTree() = default;
 
     void rotate_left(Node* subtree_root)
     {

AK/UUID.cpp

@@ -10,9 +10,6 @@
 #include <AK/UUID.h>
 
 namespace AK {
-UUID::UUID()
-{
-}
 
 UUID::UUID(Array<u8, 16> uuid_buffer)
 {

AK/UUID.h

@@ -15,7 +15,7 @@ namespace AK {
 
 class UUID {
 public:
-    UUID();
+    UUID() = default;
     UUID(Array<u8, 16> uuid_buffer);
     UUID(const StringView&);
     ~UUID() = default;

AK/Variant.h

@@ -116,7 +116,7 @@ struct VariantConstructors {
         internal_cast().set(t, VariantNoClearTag {});
     }
 
-    ALWAYS_INLINE VariantConstructors() { }
+    ALWAYS_INLINE VariantConstructors() = default;
 
 private:
     [[nodiscard]] ALWAYS_INLINE Base& internal_cast()