lightning: let ignore columns be compatible with tidb backend (#27850)

[ti-srebot]

cherry-pick #27850 to release-5.2
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/30063

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/30063:release-5.2-c68791566d55

---

What problem does this PR solve?

Let lightning config mydumper.ignore-columns be compatible with tidb backend.

Issue Number: close #xxx

Problem Summary:

What is changed and how it works?

Let the kv packend generated by encodeLoop contains the column names with ignore columns filtered instead of the raw column names.

Proposal: xxx

What's Changed:

How it Works:

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• gozssky
• kennytm

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[ti-chi-bot]

@ti-srebot: 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.

To merge this cherry pick, it must first be approved by the collaborators.

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[ti-srebot]

/run-all-tests

[ti-srebot]

@glorv you're already a collaborator in bot's repo.

[kennytm]

rest LGTM

[kennytm]

????

[sleepymole]

br/pkg/lightning/restore/restore_test.go:1517:9: assignment mismatch: 2 variables but mydump.NewCSVParser returns 1 values
br/pkg/lightning/restore/restore_test.go:1517:31: too many arguments in call to mydump.NewCSVParser

🤔

[sleepymole]

/run-check_dev

[sleepymole]

[2021-11-25T03:57:38.983Z] FAIL: restore_test.go:1445: chunkRestoreSuite.TestEncodeLoopIgnoreColumnsCSV
[2021-11-25T03:57:38.983Z] 
[2021-11-25T03:57:38.983Z] restore_test.go:1489:
[2021-11-25T03:57:38.983Z]     s.testEncodeLoopIgnoreColumnsCSV(c, cs.s, cs.ignoreColumns, cs.kvs, cs.header)
[2021-11-25T03:57:38.983Z] restore_test.go:1542:
[2021-11-25T03:57:38.983Z]     c.Assert(kvs[0].columns, DeepEquals, deliverKV.columns)
[2021-11-25T03:57:38.983Z] ... obtained []string = []string(nil)
[2021-11-25T03:57:38.983Z] ... expected []string = []string{"b", "c"}

[glorv]

/run-check_dev