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/test/validation_chainstate_tests.cpp

@@ -72,9 +72,6 @@ BOOST_AUTO_TEST_CASE(validation_chainstate_resize_caches)
         // The view cache should be empty since we had to destruct to downsize.
         BOOST_CHECK(!c1.CoinsTip().HaveCoinInCache(outpoint));
     }
-
-    // Avoid triggering the address sanitizer.
-    WITH_LOCK(::cs_main, manager.Unload());
 }
 
 //! Test UpdateTip behavior for both active and background chainstates.

src/test/validation_chainstatemanager_tests.cpp

@@ -99,8 +99,6 @@ BOOST_AUTO_TEST_CASE(chainstatemanager)
 
     // Let scheduler events finish running to avoid accessing memory that is going to be unloaded
     SyncWithValidationInterfaceQueue();
-
-    WITH_LOCK(::cs_main, manager.Unload());
 }
 
 //! Test rebalancing the caches associated with each chainstate.