wallet: Save wallet scan progress

Currently, the wallet scan progress is not saved.
If it is interrupted,  it will be necessary to start from
scratch on the next load.
With this change, progress is saved every 60 seconds.

Co-authored-by: furszy <matiasfurszyfer@protonmail.com>
Co-authored-by: Jon Atack <jon@atack.com>
Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/interfaces/chain.h

@@ -111,6 +111,10 @@ public:
     //! Get locator for the current chain tip.
     virtual CBlockLocator getTipLocator() = 0;
 
+    //! Return a locator that refers to a block in the active chain.
+    //! If specified block is not in the active chain, return locator for the latest ancestor that is in the chain.
+    virtual CBlockLocator getActiveChainLocator(const uint256& block_hash) = 0;
+
     //! Return height of the highest block on chain in common with the locator,
     //! which will either be the original block used to create the locator,
     //! or one of its ancestors.