Various enhancements to SBOR protocol

[iamyulong]

Changes:

• Renamed flag with_type to with_static_info
  • Static info includes type IDs and static sizes
  • Although, in the future, we may introduce dynamic type ID to support Any type
• Renamed read/write/check_type to read/write/check_type_id
• Split read/write_u8 into
  • read/write_variant_index
  • read/write_byte
• Added read/write_variant_label
  • In the future, we may use less bytes to represent the label size
  • May also replace label with index
• Split read/write_len into
  • read/write_dynamic_size
  • read/write_static_size
• Made Encode::encode_type_id a static function