**Describe the bug**
According to https://jira.percona.com/browse/PT-1945 and https://github.com/ClickHouse/ClickHouse/pull/21367

**Does it reproduce on a recent release?**
yep

**How to reproduce**
- define `mysql_port`
- run following SQL queries via MySQL client
```
mysql> SELECT DATABASE(), CONNECTION_ID(), VERSION()/*!50038 , @@hostname*/;
ERROR 46 (00000): Code: 46, e.displayText() = DB::Exception: Unknown function CONNECTION_ID. Maybe you meant: ['connection_id','connectionID']: While processing DATABASE(), CONNECTION_ID(), VERSION() (version 21.3.2.5 (official build))
mysql> SELECT DATABASE(), connection_id(), VERSION()/*!50038 , @@hostname*/;
ERROR 46 (00000): Code: 46, e.displayText() = DB::Exception: Unknown function VERSION. Maybe you meant: ['version']: While processing DATABASE(), connection_id(), VERSION() (version 21.3.2.5 (official build))
mysql> SELECT DATABASE(), connection_id(), version()/*!50038 , @@hostname*/;
+------------+-----------------+-----------+
| DATABASE() | connection_id() | version() |
+------------+-----------------+-----------+
| default    |               0 | 21.3.3.14  |
+------------+-----------------+-----------+
```

**Expected behavior**
VERSION() and CONNECTION_ID() aliases should work ;)

{
        return std::make_shared<FunctionVersion>();
    }
    String getName() const override
    {
        return name;
    }
    bool isDeterministic() const override { return false; }
    bool isDeterministicInScopeOfQuery() const override { return false; }
    bool isSuitableForConstantFolding() const override { return false; }
    size_t getNumberOfArguments() const override
    {
        return 0;
    }
    DataTypePtr getReturnTypeImpl(const DataTypes & ) const override
    {
        return std::make_shared<DataTypeString>();
    }
    ColumnPtr executeImpl(const ColumnsWithTypeAndName &, const DataTypePtr &, size_t input_rows_count) const override
    {
        return DataTypeString().createColumnConst(input_rows_count, VERSION_STRING);
    }
};
void registerFunctionVersion(FunctionFactory & factory)
{
    factory.registerFunction<FunctionVersion>();
}
}