Merge bitcoin/bitcoin#23003: multiprocess: Make interfaces::Chain::isTaprootActive non-const

7e88f61b285e6a356ea4f6ba384858f109559985 multiprocess: Make interfaces::Chain::isTaprootActive non-const (Russell Yanofsky)

Pull request description:

  `interfaces::Chain` is an abstract class, so declaring the method const would be exposing internal implementation details of subclasses to interface callers. And specifically this doesn't work because the multiprocess implementation of the `interfaces::Chain::isTaprootActive` method can't be const because IPC connection state and request state is not constant during the call.

  ---

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).

ACKs for top commit:
  jamesob:
    ACK 7e88f61b28

Tree-SHA512: 1c5ed89870aeb7170b9048c41299ab650dfa3d0978088e08c4c866fa0babb292722710b16f25540f26667220cb4747b1c256c4bd42893c552291eccc155346a3

src/interfaces/chain.h

@@ -289,7 +289,7 @@ public:
     virtual void requestMempoolTransactions(Notifications& notifications) = 0;
 
     //! Check if Taproot has activated
-    virtual bool isTaprootActive() const = 0;
+    virtual bool isTaprootActive() = 0;
 };
 
 //! Interface to let node manage chain clients (wallets, or maybe tools for

src/node/interfaces.cpp

@@ -698,7 +698,7 @@ public:
             notifications.transactionAddedToMempool(entry.GetSharedTx(), 0 /* mempool_sequence */);
         }
     }
-    bool isTaprootActive() const override
+    bool isTaprootActive() override
     {
         LOCK(::cs_main);
         const CBlockIndex* tip = Assert(m_node.chainman)->ActiveChain().Tip();