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.
std::set<std::string> ArgsManager::GetUnsuitableSectionOnlyArgs() const
{
    std::set<std::string> unsuitables;
    LOCK(cs_args);
    
    if (m_network.empty()) return std::set<std::string> {};
    
    if (m_network == CBaseChainParams::MAIN) return std::set<std::string> {};
    for (const auto& arg : m_network_only_args) {
        if (OnlyHasDefaultSectionSetting(m_settings, m_network, SettingName(arg))) {
            unsuitables.insert(arg);
        }
    }
    return unsuitables;
}
std::list<SectionInfo> ArgsManager::GetUnrecognizedSections() const
{
    
    static const std::set<std::string> available_sections{
        CBaseChainParams::REGTEST,
        CBaseChainParams::SIGNET,
        CBaseChainParams::TESTNET,
        CBaseChainParams::MAIN
    };
    LOCK(cs_args);
    std::list<SectionInfo> unrecognized = m_config_sections;
    unrecognized.remove_if([](const SectionInfo& appeared){ return available_sections.find(appeared.m_name) != available_sections.end(); });
    return unrecognized;
}
void ArgsManager::SelectConfigNetwork(const std::string& network)