Merge #15342: Suggested wallet code cleanups from #14711

aebafd0edf Rename Chain getLocator -> getTipLocator (Russell Yanofsky)
2c1fbaa771 Drop redundant get_value_or (Russell Yanofsky)
84adb206fc Fix ScanForWalletTransactions start_block comment (Russell Yanofsky)
2efa66b464 Document rescanblockchain returned stop_height being null (Russell Yanofsky)
db2d093233 Add suggested rescanblockchain comments (Russell Yanofsky)
a8d645c934 Update ScanForWalletTransactions result comment (Russell Yanofsky)
95a812b599 Rename ScanResult stop_block field (Russell Yanofsky)

Pull request description:

  This implements suggested changes from #14711 review comments that didn't make make it in before merging.

  There are no changes in behavior in this PR, just documentation updates, simplifications, and variable renames.

Tree-SHA512: 39f1a5718195732b70b5e427c3b3e4295ea5af6328a5991763a422051212dfb95383186db0c0504ce2c2782fb61998dfd2fe9851645b7cb4e75d849049483cc8

src/interfaces/chain.cpp

@@ -123,7 +123,7 @@ class LockImpl : public Chain::Lock
         CBlockIndex* block = LookupBlockIndex(hash);
         return block && block->GetAncestor(::chainActive.Height()) == ::chainActive.Tip();
     }
-    CBlockLocator getLocator() override { return ::chainActive.GetLocator(); }
+    CBlockLocator getTipLocator() override { return ::chainActive.GetLocator(); }
     Optional<int> findLocatorFork(const CBlockLocator& locator) override
     {
         LockAnnotation lock(::cs_main);

src/interfaces/chain.h

@@ -96,7 +96,7 @@ public:
         virtual bool isPotentialTip(const uint256& hash) = 0;
 
         //! Get locator for the current chain tip.
-        virtual CBlockLocator getLocator() = 0;
+        virtual CBlockLocator getTipLocator() = 0;
 
         //! Return height of the latest block common to locator and chain, which
         //! is guaranteed to be an ancestor of the block used to create the