Rename Chain getLocator -> getTipLocator

Suggested https://github.com/bitcoin/bitcoin/pull/14711#discussion_r252044389

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

src/wallet/wallet.cpp

@@ -4086,7 +4086,7 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
         }
 
         auto locked_chain = chain.assumeLocked();  // Temporary. Removed in upcoming lock cleanup
-        walletInstance->ChainStateFlushed(locked_chain->getLocator());
+        walletInstance->ChainStateFlushed(locked_chain->getTipLocator());
     } else if (wallet_creation_flags & WALLET_FLAG_DISABLE_PRIVATE_KEYS) {
         // Make it impossible to disable private keys after creation
         InitError(strprintf(_("Error loading %s: Private keys can only be disabled during creation"), walletFile));
@@ -4233,7 +4233,7 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
             }
         }
         walletInstance->WalletLogPrintf("Rescan completed in %15dms\n", GetTimeMillis() - nStart);
-        walletInstance->ChainStateFlushed(locked_chain->getLocator());
+        walletInstance->ChainStateFlushed(locked_chain->getTipLocator());
         walletInstance->database->IncrementUpdateCounter();
 
         // Restore wallet transaction metadata after -zapwallettxes=1