ddl: fix drop index failed when index contain auto_increment column and more than 2 index contain auto_increment_column (#12230)

[sre-bot]

cherry-pick #12230 to release-3.1

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What problem does this PR solve?

create table t (a int auto_increment,b int, unique index (a));
alter table t add index (a,b);
alter table t drop index a; – should execute successful, mysql will sucess.
(1075, u'Incorrect table definition; there can be only one auto column and it must be defined as a key')

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Code changes

• Has exported function/method change

Side effects

Related changes

• Need to cherry-pick to the release branch

Release note

• DDL: Fix the issue that drop index on auto_increment column failed when table has more than 2 indexes that contain auto_increment column.

[sre-bot]

/run-all-tests

[zz-jason]

LGTM

[jackysp]

LGTM

[sre-bot]

Your auto merge job has been accepted, waiting for 12351, 12354

[sre-bot]

/run-all-tests