Libraries: Use default constructors/destructors in LibJS

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cother-other-default-operation-rules

"The compiler is more likely to get the default semantics right and
you cannot implement these functions better than the compiler."

Author: ldm5180

Userland/Libraries/LibJS/AST.h

@@ -46,7 +46,7 @@ create_ast_node(SourceRange range, Args&&... args)
 
 class ASTNode : public RefCounted<ASTNode> {
 public:
-    virtual ~ASTNode() { }
+    virtual ~ASTNode() = default;
     virtual Completion execute(Interpreter&, GlobalObject&) const = 0;
     virtual Bytecode::CodeGenerationErrorOr<void> generate_bytecode(Bytecode::Generator&) const;
     virtual void dump(int indent) const;

Userland/Libraries/LibJS/Bytecode/Generator.cpp

@@ -19,10 +19,6 @@ Generator::Generator()
 {
 }
 
-Generator::~Generator()
-{
-}
-
 CodeGenerationErrorOr<NonnullOwnPtr<Executable>> Generator::generate(ASTNode const& node, FunctionKind enclosing_function_kind)
 {
     Generator generator;

Userland/Libraries/LibJS/Bytecode/Generator.h

@@ -194,7 +194,7 @@ class Generator {
 
 private:
     Generator();
-    ~Generator();
+    ~Generator() = default;
 
     void grow(size_t);
     void* next_slot();

Userland/Libraries/LibJS/Heap/BlockAllocator.cpp

@@ -17,10 +17,6 @@
 
 namespace JS {
 
-BlockAllocator::BlockAllocator()
-{
-}
-
 BlockAllocator::~BlockAllocator()
 {
     for (auto* block : m_blocks) {

Userland/Libraries/LibJS/Heap/BlockAllocator.h

@@ -13,7 +13,7 @@ namespace JS {
 
 class BlockAllocator {
 public:
-    BlockAllocator();
+    BlockAllocator() = default;
     ~BlockAllocator();
 
     void* allocate_block(char const* name);

Userland/Libraries/LibJS/Heap/Cell.h

@@ -19,7 +19,7 @@ class Cell {
 
 public:
     virtual void initialize(GlobalObject&) { }
-    virtual ~Cell() { }
+    virtual ~Cell() = default;
 
     bool is_marked() const { return m_mark; }
     void set_marked(bool b) { m_mark = b; }
@@ -55,7 +55,7 @@ class Cell {
     VM& vm() const;
 
 protected:
-    Cell() { }
+    Cell() = default;
 
 private:
     bool m_mark : 1 { false };

Userland/Libraries/LibJS/Heap/Heap.cpp

@@ -173,7 +173,7 @@ __attribute__((no_sanitize("address"))) void Heap::gather_conservative_roots(Has
 
 class MarkingVisitor final : public Cell::Visitor {
 public:
-    MarkingVisitor() { }
+    MarkingVisitor() = default;
 
     virtual void visit_impl(Cell& cell) override
     {

Userland/Libraries/LibJS/Interpreter.cpp

@@ -36,10 +36,6 @@ Interpreter::Interpreter(VM& vm)
 {
 }
 
-Interpreter::~Interpreter()
-{
-}
-
 // 16.1.6 ScriptEvaluation ( scriptRecord ), https://tc39.es/ecma262/#sec-runtime-semantics-scriptevaluation
 ThrowCompletionOr<Value> Interpreter::run(Script& script_record)
 {

Userland/Libraries/LibJS/Interpreter.h

@@ -101,7 +101,7 @@ class Interpreter : public Weakable<Interpreter> {
 
     static NonnullOwnPtr<Interpreter> create_with_existing_realm(Realm&);
 
-    ~Interpreter();
+    ~Interpreter() = default;
 
     ThrowCompletionOr<Value> run(Script&);
     ThrowCompletionOr<Value> run(SourceTextModule&);

Userland/Libraries/LibJS/Module.cpp

@@ -17,10 +17,6 @@ Module::Module(Realm& realm, String filename)
 {
 }
 
-Module::~Module()
-{
-}
-
 // 16.2.1.5.1.1 InnerModuleLinking ( module, stack, index ), https://tc39.es/ecma262/#sec-InnerModuleLinking
 ThrowCompletionOr<u32> Module::inner_module_linking(VM& vm, Vector<Module*>&, u32 index)
 {