Merge #11200: Allow for aborting rescans in the GUI

ae1d2b030 Give an error when rescan is aborted by the user (Andrew Chow)
69b01e6f8 Add cancel button to rescan progress dialog (Andrew Chow)

Pull request description:

  A cancel button is added to the `showProgress` dialog that is used only for rescans. When clicked, `AbortRescan` is called directly to cancel the rescan.

  Rescans triggered from the debug console will now be cancelable by clicking the cancel button.

  Rescans triggered by a command (e.g. `importmulti`) will now give an error indicating that the rescan was aborted by the user (either by the `abortrescan` command or by clicking cancel).

Tree-SHA512: 4bb14998766de686e2318fbc9805758eccf5dbe628a7257d072c9ae2fb4f61303a0876f49988d6e5eddb261969b8a307c81c0c2df0a42ae909a43d738af3dc1b

src/interfaces/wallet.cpp

@@ -130,6 +130,7 @@ public:
     {
         return m_wallet.ChangeWalletPassphrase(old_wallet_passphrase, new_wallet_passphrase);
     }
+    void abortRescan() override { m_wallet.AbortRescan(); }
     bool backupWallet(const std::string& filename) override { return m_wallet.BackupWallet(filename); }
     std::string getWalletName() override { return m_wallet.GetName(); }
     bool getKeyFromPool(bool internal, CPubKey& pub_key) override

src/interfaces/wallet.h

@@ -65,6 +65,9 @@ public:
     virtual bool changeWalletPassphrase(const SecureString& old_wallet_passphrase,
         const SecureString& new_wallet_passphrase) = 0;
 
+    //! Abort a rescan.
+    virtual void abortRescan() = 0;
+
     //! Back up wallet.
     virtual bool backupWallet(const std::string& filename) = 0;