syncer(dm) : fix default collation with upstream in create table statement (#3575)

[ti-chi-bot]

This is an automated cherry-pick of #3575

What problem does this PR solve?

fix https://github.com/pingcap/ticdc/issues/3420

in this case:
sql1: create database if not exists test
sql2: create database test CHARACTER SET=utf8mb4
sql3: create table test.t1 (id int)
sql4: create table test.t1 (id int) CHARSET=utf8mb4

if syncer send the same ddl to downstream tidb, database or table will has diffrent collation from upstream mysql, because the default collation is different between tidb and mysql.

What is changed and how it works?

it will adjust collation when sync create database or create table statement.

for database, it will add collation by binlog query event and handle ddl like these:
sql1: create database if not exists test COLLATE = utf8mb4_general_ci
sql2: create database test CHARACTER SET=utf8mb4 COLLATE = utf8mb4_general_ci

for table has no charset and collation , as we can not get collation from binlog, so there will have issue about timeliness, because dm can set start position at increment mode. so we will check and add warning log in dm.
in this case, downstream db will use collation from database for table, so user can use dm sync dabase ddl sql, but if not, user should make sure dabase's collation is right if create dabase manually. so the ddl will be handled like that:
sql3: create table test.t1 (id int) and warning log detect create table risk which use implicit charset and collation

for table has charset but no collation, we will add default collation by SHOW CHARACTER SET, so the dll will be handled like that:
sql4: create table test.t1 (id int) CHARSET=utf8mb4 COLLATE = utf8mb4_general_ci

Check List

Tests

• Unit test

Release note

Fix a bug when upstream use implicit collation in create database or create table. 
It will add collation when there is no charset and collation in create database and it will not add collation in create table as table can inherit database. 
By the way, it will not directly alter downstream schema, so that user need make sure consistence when create database or table manually.

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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[WizardXiao]

/run-all-tests

[lance6716]

/assign @nongfushanquan

[ti-chi-bot]

@ti-chi-bot: PR needs rebase.

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[lance6716]

this feature should be combined with a switch in configuration file, they will be introduced in v5.4.0