On my Linux Mint 19.1:
```bash
$ umask
0022
```

After the first run of `bitcoin-qt -sysperm=false` the `0700` permissions are expected for both the datadir (`~/.bitcoin`) and the walletdir (`~/.bitcoin/wallets`).

Actually, the directories are created with such access permissions:
```bash
$ stat ~/.bitcoin | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
$ stat ~/.bitcoin/wallets | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
```

Refs:
- #4286
- #13371
- #13389

NOTE: reading through the initial PR #4286 makes me think it was controversial. Is it a better and simpler way to just get rid of `-sysperm` option? I believe a user who needs this option can easily run `chown` command.
CURRENCY_UNIT, FormatMoney(CFeeRate{DEFAULT_PAY_TX_FEE}.GetFeePerK())), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
#ifdef ENABLE_EXTERNAL_SIGNER
    argsman.AddArg("-signer=<cmd>", "External signing tool, see doc/external-signer.md", ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
#endif
    argsman.AddArg("-spendzeroconfchange", strprintf("Spend unconfirmed change when sending transactions (default: %u)", DEFAULT_SPEND_ZEROCONF_CHANGE), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
    argsman.AddArg("-txconfirmtarget=<n>", strprintf("If paytxfee is not set, include enough fee so transactions begin confirmation on average within n blocks (default: %u)", DEFAULT_TX_CONFIRM_TARGET), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
    argsman.AddArg("-wallet=<path>", "Specify wallet path to load at startup. Can be used multiple times to load multiple wallets. Path is to a directory containing wallet data and log files. If the path is not absolute, it is interpreted relative to <walletdir>. This only loads existing wallets and does not create new ones. For backwards compatibility this also accepts names of existing top-level data files in <walletdir>.", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::WALLET);
    argsman.AddArg("-walletbroadcast",  strprintf("Make the wallet broadcast transactions (default: %u)", DEFAULT_WALLETBROADCAST), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
    argsman.AddArg("-walletdir=<dir>", "Specify directory to hold wallets (default: <datadir>/wallets if it exists, otherwise <datadir>)", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::WALLET);
#if HAVE_SYSTEM
    argsman.AddArg("-walletnotify=<cmd>", "Execute command when a wallet transaction changes. %s in cmd is replaced by TxID, %w is replaced by wallet name, %b is replaced by the hash of the block including the transaction (set to 'unconfirmed' if the transaction is not included) and %h is replaced by the block height (-1 if not included). %w is not currently implemented on windows. On systems where %w is supported, it should NOT be quoted because this would break shell escaping used to invoke the command.", ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
#endif
    argsman.AddArg("-walletrbf", strprintf("Send transactions with full-RBF opt-in enabled (RPC only, default: %u)", DEFAULT_WALLET_RBF), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
#ifdef USE_BDB
    argsman.AddArg("-dblogsize=<n>", strprintf("Flush wallet database activity from memory to disk log every <n> megabytes (default: %u)", DatabaseOptions().max_log_mb), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::WALLET_DEBUG_TEST);
    argsman.AddArg("-flushwallet", strprintf("Run a thread to flush wallet periodically (default: %u)", DEFAULT_FLUSHWALLET), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::WALLET_DEBUG_TEST);
    argsman.AddArg("-privdb", strprintf("Sets the DB_PRIVATE flag in the wallet db environment (default: %u)", !DatabaseOptions().use_shared_memory), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::WALLET_DEBUG_TEST);
#else
    argsman.AddHiddenArgs({"-dblogsize", "-flushwallet", "-privdb"});
#endif
#ifdef USE_SQLITE
    argsman.AddArg("-unsafesqlitesync", "Set SQLite synchronous=OFF to disable waiting for the database to sync to disk. This is unsafe and can cause data loss and corruption. This option is only used by tests to improve their performance (default: false)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::WALLET_DEBUG_TEST);
#else
    argsman.AddHiddenArgs({"-unsafesqlitesync"});
#endif
    argsman.AddArg("-walletrejectlongchains", strprintf("Wallet will not create transactions that violate mempool chain limits (default: %u)", DEFAULT_WALLET_REJECT_LONG_CHAINS), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::WALLET_DEBUG_TEST);
    argsman.AddArg("-walletcrosschain", strprintf("Allow reusing wallet files across chains (default: %u)", DEFAULT_WALLETCROSSCHAIN), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::WALLET_DEBUG_TEST);
    argsman.AddHiddenArgs({"-zapwallettxes"});
}
bool WalletInit::ParameterInteraction() const