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/memory/memory.go

@@ -3,6 +3,7 @@ package memory
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"s1d3sw1ped/steamcache2/vfs"
 	"s1d3sw1ped/steamcache2/vfs/locks"
@@ -35,9 +36,9 @@ type MemoryFS struct {
 }
 
 // New creates a new MemoryFS
-func New(capacity int64) *MemoryFS {
+func New(capacity int64) (*MemoryFS, error) {
 	if capacity <= 0 {
-		panic("memory capacity must be greater than 0")
+		return nil, fmt.Errorf("memory capacity must be greater than 0")
 	}
 
 	// Initialize sharded locks
@@ -51,7 +52,7 @@ func New(capacity int64) *MemoryFS {
 		keyLocks:    keyLocks,
 		LRU:         lru.NewLRUList[*types.FileInfo](),
 		timeUpdater: types.NewBatchedTimeUpdate(100 * time.Millisecond), // Update time every 100ms
-	}
+	}, nil
 }
 
 // Name returns the name of this VFS