Merge bitcoin/bitcoin#19362: rpc/blockchain: Reset scantxoutset progress before inferring descriptors

8c4129b rpc: reset scantxoutset progress on finish (Pavol Rusnak)

Pull request description:

  Fixes bitcoin/bitcoin#19361 by moving resetting the `g_scan_progress` variable **before** inferring the descriptors

ACKs for top commit:
  achow101:
    Code review ACK 8c4129b

Tree-SHA512: 2b81e5c930b9c201a1b9cc742c37e0617582326acd9adbd6b14991d33c05d51b1d5ff6a26f3accab7d274dc8c6a48bc8cbccf0811b60c1f76dd805f9b31482c0

Author: MarcoFalke

src/rpc/blockchain.cpp

@@ -2258,13 +2258,15 @@ class CoinsViewScanReserver
         if (g_scan_in_progress.exchange(true)) {
             return false;
         }
+        CHECK_NONFATAL(g_scan_progress == 0);
         m_could_reserve = true;
         return true;
     }
 
     ~CoinsViewScanReserver() {
         if (m_could_reserve) {
             g_scan_in_progress = false;
+            g_scan_progress = 0;
         }
     }
 };
@@ -2381,7 +2383,6 @@ static RPCHelpMan scantxoutset()
         std::vector<CTxOut> input_txos;
         std::map<COutPoint, Coin> coins;
         g_should_abort_scan = false;
-        g_scan_progress = 0;
         int64_t count = 0;
         std::unique_ptr<CCoinsViewCursor> pcursor;
         CBlockIndex* tip;