Merge bitcoin/bitcoin#23512: policy: Treat taproot as always active

fa3e0da06b policy: Treat taproot as always active (MarcoFalke)

Pull request description:

  Now that taproot is active, it can be treated as if it was always active for policy for the next major release. This simplifies the code and changes two things:

  * Importing `tr` descriptors can be done before the chain is fully synced. This is fine, because the wallet will already generate `tr` descriptors by default (regardless of the taproot status) after commit 47fe7445e7.
  * Valid taproot spends won't be rejected from the mempool before taproot is active. This is strictly speaking a bugfix after commit 47fe7445e7, since the wallet may generate taproot spends before the chain is fully synced. For example, a slow node or a purposefully offline node. Currently, the wallet needs the mempool to account for change. See https://github.com/bitcoin/bitcoin/issues/11887.

  A similar change was done for segwit v0 in https://github.com/bitcoin/bitcoin/pull/13120 .

  This effectively reverts commit c5ec0367d7.

ACKs for top commit:
  mjdietzx:
    Code Review ACK fa3e0da06b
  achow101:
    ACK fa3e0da06b
  sipa:
    utACK fa3e0da06b
  gruve-p:
    ACK fa3e0da06b
  gunar:
    Code Review + tACK fa3e0da06
  rajarshimaitra:
    code review + tACK fa3e0da06b

Tree-SHA512: c6dc7a4e6c345bdec33f256847dc63906ab1696aa683ab9b32a79e715613950884ac3a1a7a44e95f31bb28e58dd64679a616175f7e152b21f5550f3337c8e622

src/node/interfaces.cpp

@@ -724,12 +724,6 @@ public:
             notifications.transactionAddedToMempool(entry.GetSharedTx(), 0 /* mempool_sequence */);
         }
     }
-    bool isTaprootActive() override
-    {
-        LOCK(::cs_main);
-        const CBlockIndex* tip = Assert(m_node.chainman)->ActiveChain().Tip();
-        return DeploymentActiveAfter(tip, Params().GetConsensus(), Consensus::DEPLOYMENT_TAPROOT);
-    }
     NodeContext& m_node;
 };
 } // namespace