**Describe the bug**
When using the HTTP protocol with DateTime64 types, numerical timestamps in milliseconds do not parse correctly. This is an issue when using the Clickhouse JDBC driver with Avro Kafka records because the timestamps are integers. 

**How to reproduce**
I'm using the following CH version: yandex/clickhouse-server:20.4.5.36

Create a sample table with: 
```sql
create table tst(ts DateTime64(3)) engine TinyLog();
```

Attempt to insert millisecond timestamp into the column:
```bash
echo "1596215121682" | http -v :8123 query=="insert into tst format TSV"
```

Error:
```bash
Code: 27, e.displayText() = DB::Exception: Cannot parse input: expected '\n' before: '682\n': (at row 1)

Row 1:
Column 0,   name: ts, type: DateTime64(3), parsed text: "1596215121"
ERROR: garbage after DateTime64(3): "682<LINE FEED>"

 (version 20.4.5.36 (official build))
```

Oddly, specifying a raw query, this works:
```bash
echo 'insert into tst values(1596215121682)' | curl 'http://localhost:8123/' --data-binary @-
```
Result:
```bash
SELECT *
FROM tst

┌──────────────────────ts─┐
│ 2020-07-31 17:05:21.682 │
└─────────────────────────┘
```



**Expected behavior**
I expect to be able to insert integer millisecond timestamps using the HTTP batch insert protocol. 

Again, this issue is preventing us from using the Clickhouse JDBC driver because it fails to parse our Avro records from Kafka.

Appreciate the help!

if (from_tuple->getElements().size() != 2)
                throw Exception{"CAST AS Map from tuple requeires 2 elements.\n"
                    "Left type: " + from_tuple->getName() + ", right type: " + to_type->getName(), ErrorCodes::TYPE_MISMATCH};
            DataTypes from_kv_types;
            const auto & to_kv_types = to_type->getKeyValueTypes();
            for (const auto & elem : from_tuple->getElements())
            {
                const auto * type_array = checkAndGetDataType<DataTypeArray>(elem.get());
                if (!type_array)
                    throw Exception(ErrorCodes::TYPE_MISMATCH,
                        "CAST AS Map can only be performed from tuples of array. Got: {}", from_tuple->getName());
                from_kv_types.push_back(type_array->getNestedType());
            }
            return createTupleToMapWrapper(from_kv_types, to_kv_types);
        }
        else if (const auto * from_array = typeid_cast<const DataTypeArray *>(from_type_untyped.get()))
        {
            const auto * nested_tuple = typeid_cast<const DataTypeTuple *>(from_array->getNestedType().get());
            if (!nested_tuple || nested_tuple->getElements().size() != 2)
                throw Exception{"CAST AS Map from array requeires nested tuple of 2 elements.\n"
                    "Left type: " + from_array->getName() + ", right type: " + to_type->getName(), ErrorCodes::TYPE_MISMATCH};
            return createArrayToMapWrrapper(nested_tuple->getElements(), to_type->getKeyValueTypes());
        }
        else if (const auto * from_type = checkAndGetDataType<DataTypeMap>(from_type_untyped.get()))
        {
            return createMapToMapWrrapper(from_type->getKeyValueTypes(), to_type->getKeyValueTypes());
        }
        else
        {
            throw Exception{"Unsupported types to CAST AS Map\n"