Remove useless fields in TiDB::TableInfo

[JaySon-Huang]

Enhancement

The serialized result of TiDB::TableInfo contains too many useless fields when they are "empty". We can remove them to shorten the serialized output and make the result more clear for debug and writing test cases.

• "comment"
• "partition"
• origin_default_bit_value/origin_default/default/default_bit/type.{Charset,Collate,Elems} in the "ColumnInfo"

tiflash/dbms/src/TiDB/tests/gtest_table_info.cpp

Lines 193 to 194 in 881a80d

R"json({"id":1145,"name":{"O":"customerdebt","L":"customerdebt"},"cols":[{"id":1,"name":{"O":"id","L":"id"},"offset":0,"origin_default":null,"default":null,"default_bit":null,"type":{"Tp":8,"Flag":515,"Flen":20,"Decimal":0},"state":5,"comment":"i\"d"}],"state":5,"pk_is_handle":true,"schema_version":-1,"comment":"负债信息","partition":null})json", //

R"stmt(CREATE TABLE `db_1939`.`t_1145`(`id` Int64) Engine = DeltaMerge((`id`), '{"cols":[{"comment":"i\\"d","default":null,"default_bit":null,"id":1,"name":{"L":"id","O":"id"},"offset":0,"origin_default":null,"state":5,"type":{"Charset":null,"Collate":null,"Decimal":0,"Elems":null,"Flag":515,"Flen":20,"Tp":8}}],"comment":"\\u8D1F\\u503A\\u4FE1\\u606F","id":1145,"index_info":[],"is_common_handle":false,"keyspace_id":4294967295,"name":{"L":"customerdebt","O":"customerdebt"},"partition":null,"pk_is_handle":true,"schema_version":-1,"state":5,"tiflash_replica":{"Count":0},"update_timestamp":0}', 0))stmt", //