feat(interactive): Import VARCHAR to GraphScope interactive

[zhanglei1949]

Import a new data type VARCHAR to GraphScope Interactive.
#3400
#3405

0. Use VARCHAR in schema. VARCHAR is not a primitive type.

The following Representation can be revised.

property_type:
  var_char:
    max_length: 128

1. Refactor PropertyType

Previous PropertyType is just a enum.

enum class PropertyType {
  kEmpty,
  kBool,
  kUInt8,
  kUInt16,
  ...
};

To represent VARCHAR, an enum alone is not enough, because we also need to express the maximum length of VARCHAR, i.e. max_length.

namespace impl {

enum class PropertyTypeImpl {
  kEmpty,
  kBool,
  kUInt8,
  kUInt16,
 ...
};

// Stores additional type information for PropertyTypeImpl
union AdditionalTypeInfo {
  uint16_t max_length;  // for varchar
};
}  // namespace impl

struct PropertyType {
  impl::PropertyTypeImpl type_enum;
  impl::AdditionalTypeInfo additional_type_info;

  PropertyType()
      : type_enum(impl::PropertyTypeImpl::kEmpty), additional_type_info() {}
  PropertyType(impl::PropertyTypeImpl type)
      : type_enum(type), additional_type_info() {}
  PropertyType(impl::PropertyTypeImpl type, uint16_t max_length)
      : type_enum(type), additional_type_info({.max_length = max_length}) {
    assert(type == impl::PropertyTypeImpl::kVarChar);
  }

  //get DataType object, like `arrow::bool()`(but arrow returns a shared_ptr)
  static PropertyType empty();
  static PropertyType bool_();
  static PropertyType uint8();
  static PropertyType uint16();

  // different from other functions
  static PropertyType var_char(uint16_t max_length); 
  //...

  static const PropertyType kEmpty;
  static const PropertyType kBool;
  static const PropertyType kUInt8;
  static const PropertyType kUInt16;
  //...

  bool operator==(const PropertyType& other) const;
  bool operator!=(const PropertyType& other) const;
};