fix restore auto increment ID overflow

[3pointer]

What problem does this PR solve?

when auto_increment id reached max.Int64, it can backs up success. but failed when restore. we should handle this situation.

What is changed and how it works?

if autoIncID overflowed. change is to max.Int64, to keep consistency with backup cluster.

Check List

Tests

• Integration test

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch

Release Note

• No release note

[kennytm]

what about bigint unsigned columns?

createtablea (id bigint unsigned primary key auto_increment);
insert into a values (12345678901234567890);

[3pointer]

I was wondering that the allocator can work well 🤔️，it set the allocator with unsigned=false https://github.com/pingcap/br/blob/master/pkg/backup/client.go#L261

[3pointer]

How about add globalAutoID -= 1 after https://github.com/pingcap/br/blob/master/pkg/backup/client.go#L277?

[kennytm]

I'm not sure what's the purpose of subtracting 1 😅

[overvenus]

Any update?

[3pointer]

/run-integration-tests

[kennytm]

rest LGTM

[kennytm]

the two branches are the same? so this is simply

 }
autoIncID=uint64(table.Info.AutoIncID)

?