Merge bitcoin/bitcoin#24050: validation: Give m_block_index ownership of CBlockIndexs

6c23c41561 refactor: Rewrite AddToBlockIndex with try_emplace (Carl Dong)
c05cf7aa1e style: Modernize range-based loops over m_block_index (Carl Dong)
c2a1655799 style-only: Use using instead of typedef for BlockMap (Carl Dong)
dd79dad175 refactor: Rewrite InsertBlockIndex with try_emplace (Carl Dong)
531dce0347 tests: Remove now-unnecessary manual Unload's (Carl Dong)
bec86ae326 blockstorage: Make m_block_index own CBlockIndex's (Carl Dong)

Pull request description:

  Part of: #24303
  Split off from: #22564

  ```
  Instead of having CBlockIndex's live on the heap, which requires manual
  memory management, have them be owned by m_block_index. This means that
  they will live and die with BlockManager.
  ```

  The second commit demonstrates how this makes calls to `Unload()` to satisfy the address sanitizer unnecessary.

ACKs for top commit:
  ajtowns:
    ACK 6c23c41561
  MarcoFalke:
    re-ACK 6c23c41561 🎨

Tree-SHA512: 81b2b5119be27cc0f8a9457b11da60cc60930315d2a5be36be89fe253d32073ffe622348ff153114b9b3212197bddbc791810913a43811b33cc58e7162bd105b

src/rpc/blockchain.cpp

@@ -1753,10 +1753,10 @@ static RPCHelpMan getchaintips()
     std::set<const CBlockIndex*> setOrphans;
     std::set<const CBlockIndex*> setPrevs;
 
-    for (const std::pair<const uint256, CBlockIndex*>& item : chainman.BlockIndex()) {
-        if (!active_chain.Contains(item.second)) {
-            setOrphans.insert(item.second);
-            setPrevs.insert(item.second->pprev);
+    for (const auto& [_, block_index] : chainman.BlockIndex()) {
+        if (!active_chain.Contains(&block_index)) {
+            setOrphans.insert(&block_index);
+            setPrevs.insert(block_index.pprev);
         }
     }