Everywhere: Switch from (void) to [[maybe_unused]] (#4473)

Problem:
- `(void)` simply casts the expression to void. This is understood to
  indicate that it is ignored, but this is really a compiler trick to
  get the compiler to not generate a warning.

Solution:
- Use the `[[maybe_unused]]` attribute to indicate the value is unused.

Note:
- Functions taking a `(void)` argument list have also been changed to
  `()` because this is not needed and shows up in the same grep
  command.

Kernel/VM/InodeVMObject.cpp

@@ -89,10 +89,8 @@ void InodeVMObject::inode_size_changed(Badge<Inode>, size_t old_size, size_t new
     });
 }
 
-void InodeVMObject::inode_contents_changed(Badge<Inode>, off_t offset, ssize_t size, const UserOrKernelBuffer& data)
+void InodeVMObject::inode_contents_changed(Badge<Inode>, off_t offset, [[maybe_unused]] ssize_t size, [[maybe_unused]] const UserOrKernelBuffer& data)
 {
-    (void)size;
-    (void)data;
     InterruptDisabler disabler;
     ASSERT(offset >= 0);