Enhance DiskFS initialization and error handling

- Updated `disk.New` to support asynchronous initialization for large caches, improving responsiveness during startup.
- Introduced an eviction function parameter to `disk.New`, ensuring proper handling of over-capacity scenarios.
- Enhanced error handling in various components, including memory and disk tests, to ensure robustness and clarity.
- Refactored tests to validate new behaviors, including checks for delayed attachment and proper error propagation.
- Removed obsolete error handling code and tests related to the now-deleted errors package, streamlining the codebase.

vfs/cache/cache_test.go

@@ -11,8 +11,14 @@ import (
 
 func TestTieredCache_PromotionFallback(t *testing.T) {
 	t.Parallel()
-	fast := memory.New(1 * 1024 * 1024)
-	slow := memory.New(10 * 1024 * 1024) // use mem for "disk" in test
+	fast, err := memory.New(1 * 1024 * 1024)
+	if err != nil {
+		t.Fatal(err)
+	}
+	slow, err := memory.New(10 * 1024 * 1024) // use mem for "disk" in test
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	tc := New()
 	tc.SetFast(fast)
@@ -59,8 +65,14 @@ func TestTieredCache_PromotionFallback(t *testing.T) {
 
 func TestTieredCache_DeleteAllTiers(t *testing.T) {
 	t.Parallel()
-	fast := memory.New(1024)
-	slow := memory.New(1024)
+	fast, err := memory.New(1024)
+	if err != nil {
+		t.Fatal(err)
+	}
+	slow, err := memory.New(1024)
+	if err != nil {
+		t.Fatal(err)
+	}
 	tc := New()
 	tc.SetFast(fast)
 	tc.SetSlow(slow)
@@ -80,8 +92,14 @@ func TestTieredCache_Concurrent(t *testing.T) {
 		t.Skip()
 	}
 	t.Parallel()
-	fast := memory.New(5 * 1024 * 1024)
-	slow := memory.New(20 * 1024 * 1024)
+	fast, err := memory.New(5 * 1024 * 1024)
+	if err != nil {
+		t.Fatal(err)
+	}
+	slow, err := memory.New(20 * 1024 * 1024)
+	if err != nil {
+		t.Fatal(err)
+	}
 	tc := New()
 	tc.SetFast(fast)
 	tc.SetSlow(slow)