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/gc/gc_test.go

@@ -7,7 +7,10 @@ import (
 
 func TestGCFS_BasicEvictOnCreate(t *testing.T) {
 	t.Parallel()
-	m := memory.New(400)
+	m, err := memory.New(400)
+	if err != nil {
+		t.Fatal(err)
+	}
 	g := New(m, LRU)
 
 	// Fill over
@@ -27,7 +30,10 @@ func TestGCFS_BasicEvictOnCreate(t *testing.T) {
 
 func TestAsyncGCFS_Stop(t *testing.T) {
 	t.Parallel()
-	m := memory.New(1 << 20)
+	m, err := memory.New(1 << 20)
+	if err != nil {
+		t.Fatal(err)
+	}
 	ag := NewAsync(m, LRU, true, 0.7, 0.9, 1.0)
 	// do some creates
 	for i := 0; i < 3; i++ {
@@ -46,7 +52,10 @@ func TestAsyncGCFS_Stop(t *testing.T) {
 
 func TestGCFS_ForceAndStats(t *testing.T) {
 	t.Parallel()
-	m := memory.New(500)
+	m, err := memory.New(500)
+	if err != nil {
+		t.Fatal(err)
+	}
 	g := New(m, LRU)
 	w, _ := g.Create("f", 400)
 	w.Write(make([]byte, 400))
@@ -66,7 +75,10 @@ func TestGCFS_ForceAndStats(t *testing.T) {
 // TestAsyncGCFS_QueuedAndDoubleStop exercises queueing, running flag, double-stop (issue8 coverage).
 func TestAsyncGCFS_QueuedAndDoubleStop(t *testing.T) {
 	t.Parallel()
-	m := memory.New(1 << 20)
+	m, err := memory.New(1 << 20)
+	if err != nil {
+		t.Fatal(err)
+	}
 	ag := NewAsync(m, LRU, true, 0.5, 0.8, 1.0)
 	defer ag.Stop()