planner: remove the limitation that predicates can't be pushed through Projection on TableDual (#51329)

[ti-chi-bot]

This is an automated cherry-pick of #51329

What problem does this PR solve?

Issue Number: close #50614

Problem Summary:

#35669 disables predicates pushdown on TableDual.
This usually won't cause problems, but when it comes to cases like #50614, many unnecessary predicates with lots of conditions will cause obvious performance regression.

What changed and how does it work?

This PR reverts #35669, which is for fixing #35527.
#35527 itself has already been fixed by #38802, which prevents predicates from being incorrectly pushed through Projection.

As said in #35669, sometimes TableDual doesn't have a schema. This may or may not be considered as a mistake depending on our definition of the semantic of TableDual.
Anyway, TableDual without schema should not cause a problem if the predicates are pushed down correctly.

Check List

Tests

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

  • I checked and no code files have been changed.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

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[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

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[time-and-fate]

Already cherry-picked in #52164

[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/build	e8ad174	link	true	/test build
idc-jenkins-ci-tidb/check_dev_2	e8ad174	link	true	/test check-dev2
idc-jenkins-ci-tidb/check_dev	e8ad174	link	true	/test check-dev

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