Merge bitcoin/bitcoin#24515: Only load BlockMan in BlockMan member functions

f865cf8ded Add and use BlockManager::GetAllBlockIndices (Carl Dong)
28ba0313ea Add and use CBlockIndexHeightOnlyComparator (Carl Dong)
12eb05df63 move-only: Move CBlockIndexWorkComparator to blockstorage (Carl Dong)
c600ee3816 Only load BlockMan in BlockMan member functions (Carl Dong)
42e56d9b18 style-only: No need for std::pair for vSortedByHeight (Carl Dong)
3bbb6fea05 style-only: Various blockstorage.cpp cleanups (Carl Dong)
5be9ee3c54 refactor: more const annotations for uses of CBlockIndex* (Anthony Towns)

Pull request description:

  The only important commit is "Only load BlockMan in BlockMan member functions", everything else is all just small style changes.

  Here's the commit message, reproduced:
  ```
  This commit effectively splits the "load block index itself" logic from
  "derive Chainstate variables from loaded block index" logic.

  This means that BlockManager::LoadBlockIndex{,DB} will only load what's
  relevant to the BlockManager.
  ```

ACKs for top commit:
  ajtowns:
    ACK f865cf8ded ; code review only
  MarcoFalke:
    review ACK f865cf8ded 🗂

Tree-SHA512: 7b204d782834e06fd7329d022e2ae860181b4e8105c33bfb928539a4ec24161dc7438a9c4d4ee279dcad77de310c160b997bb8aa18923243d0fd55ccf4ad7c3a

src/rest.cpp

@@ -284,8 +284,8 @@ static bool rest_block(const std::any& context,
         return RESTERR(req, HTTP_BAD_REQUEST, "Invalid hash: " + hashStr);
 
     CBlock block;
-    CBlockIndex* pblockindex = nullptr;
-    CBlockIndex* tip = nullptr;
+    const CBlockIndex* pblockindex = nullptr;
+    const CBlockIndex* tip = nullptr;
     {
         ChainstateManager* maybe_chainman = GetChainman(context, req);
         if (!maybe_chainman) return false;