[build] Move wallet load functions to wallet/load unit

Moves the following wallet load functions to a new wallet/load unit in
the libbitcoin_wallet library. All other functions in wallet/init remain
in libbitcoin_server:

- `VerifyWallets`
- `LoadWallets`
- `StartWallets`
- `FlushWallets`
- `StopWallets`
- `UnloadWallets`

src/wallet/init.cpp

@@ -131,58 +131,6 @@ bool WalletInit::ParameterInteraction() const
     return true;
 }
 
-bool VerifyWallets(interfaces::Chain& chain, const std::vector<std::string>& wallet_files)
-{
-    if (gArgs.IsArgSet("-walletdir")) {
-        fs::path wallet_dir = gArgs.GetArg("-walletdir", "");
-        boost::system::error_code error;
-        // The canonical path cleans the path, preventing >1 Berkeley environment instances for the same directory
-        fs::path canonical_wallet_dir = fs::canonical(wallet_dir, error);
-        if (error || !fs::exists(wallet_dir)) {
-            chain.initError(strprintf(_("Specified -walletdir \"%s\" does not exist"), wallet_dir.string()));
-            return false;
-        } else if (!fs::is_directory(wallet_dir)) {
-            chain.initError(strprintf(_("Specified -walletdir \"%s\" is not a directory"), wallet_dir.string()));
-            return false;
-        // The canonical path transforms relative paths into absolute ones, so we check the non-canonical version
-        } else if (!wallet_dir.is_absolute()) {
-            chain.initError(strprintf(_("Specified -walletdir \"%s\" is a relative path"), wallet_dir.string()));
-            return false;
-        }
-        gArgs.ForceSetArg("-walletdir", canonical_wallet_dir.string());
-    }
-
-    LogPrintf("Using wallet directory %s\n", GetWalletDir().string());
-
-    chain.initMessage(_("Verifying wallet(s)..."));
-
-    // Parameter interaction code should have thrown an error if -salvagewallet
-    // was enabled with more than wallet file, so the wallet_files size check
-    // here should have no effect.
-    bool salvage_wallet = gArgs.GetBoolArg("-salvagewallet", false) && wallet_files.size() <= 1;
-
-    // Keep track of each wallet absolute path to detect duplicates.
-    std::set<fs::path> wallet_paths;
-
-    for (const auto& wallet_file : wallet_files) {
-        WalletLocation location(wallet_file);
-
-        if (!wallet_paths.insert(location.GetPath()).second) {
-            chain.initError(strprintf(_("Error loading wallet %s. Duplicate -wallet filename specified."), wallet_file));
-            return false;
-        }
-
-        std::string error_string;
-        std::string warning_string;
-        bool verify_success = CWallet::Verify(chain, location, salvage_wallet, error_string, warning_string);
-        if (!error_string.empty()) chain.initError(error_string);
-        if (!warning_string.empty()) chain.initWarning(warning_string);
-        if (!verify_success) return false;
-    }
-
-    return true;
-}
-
 void WalletInit::Construct(InitInterfaces& interfaces) const
 {
     if (gArgs.GetBoolArg("-disablewallet", DEFAULT_DISABLE_WALLET)) {
@@ -192,52 +140,3 @@ void WalletInit::Construct(InitInterfaces& interfaces) const
     gArgs.SoftSetArg("-wallet", "");
     interfaces.chain_clients.emplace_back(interfaces::MakeWalletClient(*interfaces.chain, gArgs.GetArgs("-wallet")));
 }
-
-bool LoadWallets(interfaces::Chain& chain, const std::vector<std::string>& wallet_files)
-{
-    for (const std::string& walletFile : wallet_files) {
-        std::shared_ptr<CWallet> pwallet = CWallet::CreateWalletFromFile(chain, WalletLocation(walletFile));
-        if (!pwallet) {
-            return false;
-        }
-        AddWallet(pwallet);
-    }
-
-    return true;
-}
-
-void StartWallets(CScheduler& scheduler)
-{
-    for (const std::shared_ptr<CWallet>& pwallet : GetWallets()) {
-        pwallet->postInitProcess();
-    }
-
-    // Schedule periodic wallet flushes and tx rebroadcasts
-    scheduler.scheduleEvery(MaybeCompactWalletDB, 500);
-    scheduler.scheduleEvery(MaybeResendWalletTxs, 1000);
-}
-
-void FlushWallets()
-{
-    for (const std::shared_ptr<CWallet>& pwallet : GetWallets()) {
-        pwallet->Flush(false);
-    }
-}
-
-void StopWallets()
-{
-    for (const std::shared_ptr<CWallet>& pwallet : GetWallets()) {
-        pwallet->Flush(true);
-    }
-}
-
-void UnloadWallets()
-{
-    auto wallets = GetWallets();
-    while (!wallets.empty()) {
-        auto wallet = wallets.back();
-        wallets.pop_back();
-        RemoveWallet(wallet);
-        UnloadWallet(std::move(wallet));
-    }
-}