Merge ibd-sync-speedups into dev

Parallel RandomX PoW pre-verify, adaptive dbcache, UTXO snapshot, P2P/TLS sync fixes.

src/chain.h

@@ -399,7 +399,16 @@ public:
 
     //! (memory only) Sequential id assigned to distinguish order in which blocks are received.
     uint32_t nSequenceId;
-    
+
+    //! (memory only) Set true once this block's RandomX PoW has been verified by the parallel
+    //! pre-verification pool, letting the inline check in CheckBlockHeader skip the recompute.
+    //! Written by exactly one pre-verify worker (1:1 with the block) and read by the connect
+    //! thread only AFTER the pool barrier (CCheckQueue::Wait provides the happens-before), so a
+    //! plain bool is race-free here. NOT serialized — a pure optimization hint; the inline
+    //! CheckRandomXSolution remains the consensus authority. (Plain bool, not std::atomic, so
+    //! CBlockIndex stays copyable for CDiskBlockIndex's `CBlockIndex(*pindex)` construction.)
+    bool fRandomXVerified;
+
     void SetNull()
     {
         phashBlock = NULL;
@@ -414,6 +423,7 @@ public:
         chainPower = CChainPower();
         nTx = 0;
         nChainTx = 0;
+        fRandomXVerified = false;
 
         // Shieldex Index chain stats
         nChainPayments = 0;