Merge #18698: Make g_chainman internal to validation

fab6b9d18f validation: Mark g_chainman DEPRECATED (MarcoFalke)
fa1d97b256 validation: Make ProcessNewBlock*() members of ChainstateManager (MarcoFalke)
fa24d49098 validation: Make PruneOneBlockFile() a member of ChainstateManager (MarcoFalke)
fa84b1cd84 validation: Make LoadBlockIndex() a member of ChainstateManager (MarcoFalke)
fa05fdf0f1 net: Pass chainman into PeerLogicValidation (MarcoFalke)
fa7b626d7a node: Add chainman alias for g_chainman (MarcoFalke)

Pull request description:

  The global `g_chainman` has recently been introduced in #17737. The chainstate manager is primarily needed for the assumeutxo feature, but it can also simplify testing in the future.

  The goal of this pull is to make the global chainstate manager internal to validation, so that all external code does not depend on globals and that unit or fuzz tests can pass in their (potentially mocked) chainstate manager.

  I suggest reviewing the pull request commit-by-commit. It should be relatively straightforward refactoring that does not change behavior at all.

ACKs for top commit:
  ryanofsky:
    Code review ACK fab6b9d18f. Had to be rebased but still looks good

Tree-SHA512: dcbf114aeef4f8320d466369769f22ce4dd8f46a846870354df176c3de9ff17c64630fbd777e7121d7470d7a8564ed8d37b77168746e8df7489c6877e55d7b4f

src/rpc/blockchain.cpp

@@ -71,6 +71,12 @@ CTxMemPool& EnsureMemPool(const util::Ref& context)
     return *node.mempool;
 }
 
+ChainstateManager& EnsureChainman(const util::Ref& context)
+{
+    NodeContext& node = EnsureNodeContext(context);
+    return EnsureChainman(node);
+}
+
 /* Calculate the difficulty for a given block index.
  */
 double GetDifficulty(const CBlockIndex* blockindex)