[global-handles] Refactor to allow for different node type

- Introduce NodeSpace that holds allocation related logic.
- Provide std compatible iterator for node iteration.

This allows for creating a different internal node type.

The change is just a refactoring without functional changes.

Bug: chromium:923361
Change-Id: I424f821d96b3a82f64024aedff6c289d3eec11a2
Reviewed-on: https://chromium-review.googlesource.com/c/1418192
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58931}

src/global-handles.h

@@ -185,8 +185,12 @@ class GlobalHandles {
  private:
   // Internal node structures.
   class Node;
+  template <class NodeType>
   class NodeBlock;
+  template <class BlockType>
   class NodeIterator;
+  template <class NodeType>
+  class NodeSpace;
   class PendingPhantomCallback;
 
   explicit GlobalHandles(Isolate* isolate);
@@ -201,15 +205,7 @@ class GlobalHandles {
 
   Isolate* isolate_;
 
-  // List of all allocated node blocks.
-  NodeBlock* first_block_;
-
-  // List of node blocks with used nodes.
-  NodeBlock* first_used_block_;
-
-  // Free list of nodes.
-  Node* first_free_;
-
+  std::unique_ptr<NodeSpace<Node>> regular_nodes_;
   // Contains all nodes holding new space objects. Note: when the list
   // is accessed, some of the objects may have been promoted already.
   std::vector<Node*> new_space_nodes_;