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/FileSystem/BlockBasedFileSystem.cpp

@@ -114,9 +114,7 @@ BlockBasedFileSystem::BlockBasedFileSystem(OpenFileDescription& file_description
     VERIFY(file_description.file().is_seekable());
 }
 
-BlockBasedFileSystem::~BlockBasedFileSystem()
-{
-}
+BlockBasedFileSystem::~BlockBasedFileSystem() = default;
 
 ErrorOr<void> BlockBasedFileSystem::initialize()
 {