AK: Use AK_MAKE_DEFAULT_MOVABLE to avoid mistakes in default impls

Author: https://github.com/BenWiederhake
Commit: 041f5e931d
Pull-request: https://github.com/SerenityOS/serenity/pull/19422

AK/BufferedStream.h

@@ -21,6 +21,7 @@ concept SeekableStreamLike = IsBaseOf<SeekableStream, T>;
 template<typename T>
 class BufferedHelper {
     AK_MAKE_NONCOPYABLE(BufferedHelper);
+    AK_MAKE_DEFAULT_MOVABLE(BufferedHelper);
 
 public:
     template<StreamLike U>
@@ -30,19 +31,6 @@ public:
     {
     }
 
-    BufferedHelper(BufferedHelper&& other)
-        : m_stream(move(other.m_stream))
-        , m_buffer(move(other.m_buffer))
-    {
-    }
-
-    BufferedHelper& operator=(BufferedHelper&& other)
-    {
-        m_stream = move(other.m_stream);
-        m_buffer = move(other.m_buffer);
-        return *this;
-    }
-
     template<template<typename> typename BufferedType>
     static ErrorOr<NonnullOwnPtr<BufferedType<T>>> create_buffered(NonnullOwnPtr<T> stream, size_t buffer_size)
     {

AK/CircularBuffer.h

@@ -15,14 +15,12 @@ namespace AK {
 
 class CircularBuffer {
     AK_MAKE_NONCOPYABLE(CircularBuffer);
+    AK_MAKE_DEFAULT_MOVABLE(CircularBuffer);
 
 public:
     static ErrorOr<CircularBuffer> create_empty(size_t size);
     static ErrorOr<CircularBuffer> create_initialized(ByteBuffer);
 
-    CircularBuffer(CircularBuffer&& other) = default;
-    CircularBuffer& operator=(CircularBuffer&& other) = default;
-
     ~CircularBuffer() = default;
 
     size_t write(ReadonlyBytes bytes);

AK/SourceGenerator.h

@@ -36,6 +36,8 @@ public:
     }
 
     SourceGenerator(SourceGenerator&&) = default;
+    // Move-assign is undefinable due to 'StringBuilder& m_builder;'
+    SourceGenerator& operator=(SourceGenerator&&) = delete;
 
     ErrorOr<SourceGenerator> fork()
     {