Kernel: Use default constructors/destructors

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."

Kernel/Memory/AddressSpace.cpp

@@ -29,9 +29,7 @@ AddressSpace::AddressSpace(NonnullRefPtr<PageDirectory> page_directory)
 {
 }
 
-AddressSpace::~AddressSpace()
-{
-}
+AddressSpace::~AddressSpace() = default;
 
 ErrorOr<void> AddressSpace::unmap_mmap_range(VirtualAddress addr, size_t size)
 {

Kernel/Memory/AnonymousVMObject.cpp

@@ -166,9 +166,7 @@ AnonymousVMObject::AnonymousVMObject(AnonymousVMObject const& other, NonnullRefP
 {
 }
 
-AnonymousVMObject::~AnonymousVMObject()
-{
-}
+AnonymousVMObject::~AnonymousVMObject() = default;
 
 size_t AnonymousVMObject::purge()
 {
@@ -370,9 +368,7 @@ AnonymousVMObject::SharedCommittedCowPages::SharedCommittedCowPages(CommittedPhy
 {
 }
 
-AnonymousVMObject::SharedCommittedCowPages::~SharedCommittedCowPages()
-{
-}
+AnonymousVMObject::SharedCommittedCowPages::~SharedCommittedCowPages() = default;
 
 NonnullRefPtr<PhysicalPage> AnonymousVMObject::SharedCommittedCowPages::take_one()
 {

Kernel/Memory/InodeVMObject.cpp

@@ -25,9 +25,7 @@ InodeVMObject::InodeVMObject(InodeVMObject const& other, FixedArray<RefPtr<Physi
         m_dirty_pages.set(i, other.m_dirty_pages.get(i));
 }
 
-InodeVMObject::~InodeVMObject()
-{
-}
+InodeVMObject::~InodeVMObject() = default;
 
 size_t InodeVMObject::amount_clean() const
 {

Kernel/Memory/MemoryManager.cpp

@@ -94,9 +94,7 @@ UNMAP_AFTER_INIT MemoryManager::MemoryManager()
     m_lazy_committed_page = committed_pages.take_one();
 }
 
-UNMAP_AFTER_INIT MemoryManager::~MemoryManager()
-{
-}
+UNMAP_AFTER_INIT MemoryManager::~MemoryManager() = default;
 
 UNMAP_AFTER_INIT void MemoryManager::protect_kernel_image()
 {

Kernel/Memory/PageDirectory.cpp

@@ -123,9 +123,7 @@ ErrorOr<NonnullRefPtr<PageDirectory>> PageDirectory::try_create_for_userspace(Vi
     return directory;
 }
 
-PageDirectory::PageDirectory()
-{
-}
+PageDirectory::PageDirectory() = default;
 
 UNMAP_AFTER_INIT void PageDirectory::allocate_kernel_directory()
 {

Kernel/Memory/PhysicalRegion.cpp

@@ -27,9 +27,7 @@ static constexpr u32 next_power_of_two(u32 value)
     return value;
 }
 
-PhysicalRegion::~PhysicalRegion()
-{
-}
+PhysicalRegion::~PhysicalRegion() = default;
 
 PhysicalRegion::PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper)
     : m_lower(lower)

Kernel/Memory/PrivateInodeVMObject.cpp

@@ -33,8 +33,6 @@ PrivateInodeVMObject::PrivateInodeVMObject(PrivateInodeVMObject const& other, Fi
 {
 }
 
-PrivateInodeVMObject::~PrivateInodeVMObject()
-{
-}
+PrivateInodeVMObject::~PrivateInodeVMObject() = default;
 
 }