dont bulk load for table metadata change

[luqun]

Summary:

When customer issue a DDL statement, it will change a table's metadata(whose data is stored in DD) and a tables' raw data.

• during table metadata change, DD will enable OPTION_DD_UPDATE_CONTEXT flag(https://github.com/facebook/mysql-5.6/blob/fb-mysql-8.0.28/sql/dd/impl/transaction_impl.cc#L169).

• during table raw data change, OPTION_DD_UPDATE_CONTEXT flag isn't enabled.

if current DD is myrocks and customer try to run a DDL with bulk loading enabled,

• before this change, myrocks write table metadata using bulk loading when DD save new schema(such as dd::Table_impl::store_children). Later, DD will try to read new schema(such as dd::Table_impl::restore_children), then it fail to find new schema due myrocks bulk load doesn't support read your own data.

• after this change, table metadata won't use bulk loading(its change data is small) and current trx can read its own data.

Test Plan:

Reviewers:

Subscribers:

Tasks:

Tags:

[luqun]

@laurynas-biveinis , I will commit this PR today if it looks okay to you.

[laurynas-biveinis]

@laurynas-biveinis , I will commit this PR today if it looks okay to you.

Please add const to the method definition (now only declaration has it), and then go ahead 👍