Move Weak type to Helpers module

Author: Guilherme Souza

Sources/Realtime/V2/Weak.swift renamed to Sources/Helpers/Weak.swift

@@ -7,16 +7,16 @@
 
 import Foundation
 
-final class Weak<T: AnyObject & Sendable>: @unchecked Sendable {
+package final class Weak<T: AnyObject & Sendable>: @unchecked Sendable {
   let lock = NSRecursiveLock()
   private weak var _value: T?
 
-  var value: T? {
+  package var value: T? {
     get { lock.withLock { _value } }
     set { lock.withLock { _value = newValue } }
   }
 
-  init(_ value: T?) {
+  package init(_ value: T?) {
     _value = value
   }
 }