Kernel: Remove FIFO::{attach,detach}(Direction)

These functions would have caused a `-Woverloaded-virtual` warning with
GCC 13, as they shadow `File::{attach,detach}(OpenFileDescription&)`.

Both of these functions had a single call site. This commit inlines
`attach` into its only caller, `FIFO::open_direction`.

Instead of explicitly checking `is_fifo()` in `~OpenFileDescription`
before running the `detach(Direction)` overload, let's just override the
regular `detach(OpenFileDescription&)` for `FIFO` to perform this action
instead.

Kernel/FileSystem/FIFO.cpp

@@ -25,7 +25,12 @@ ErrorOr<NonnullRefPtr<FIFO>> FIFO::try_create(UserID uid)
 ErrorOr<NonnullRefPtr<OpenFileDescription>> FIFO::open_direction(FIFO::Direction direction)
 {
     auto description = TRY(OpenFileDescription::try_create(*this));
-    attach(direction);
+    if (direction == Direction::Reader) {
+        ++m_readers;
+    } else if (direction == Direction::Writer) {
+        ++m_writers;
+    }
+    evaluate_block_conditions();
     description->set_fifo_direction({}, direction);
     return description;
 }
@@ -73,19 +78,11 @@ FIFO::FIFO(UserID uid, NonnullOwnPtr<DoubleBuffer> buffer)
 
 FIFO::~FIFO() = default;
 
-void FIFO::attach(Direction direction)
+void FIFO::detach(OpenFileDescription& description)
 {
-    if (direction == Direction::Reader) {
-        ++m_readers;
-    } else if (direction == Direction::Writer) {
-        ++m_writers;
-    }
+    File::detach(description);
 
-    evaluate_block_conditions();
-}
-
-void FIFO::detach(Direction direction)
-{
+    auto direction = description.fifo_direction();
     if (direction == Direction::Reader) {
         VERIFY(m_readers);
         --m_readers;