planner: introduce Cond-FD to maintain null-constraint FD (#34147)

[ti-srebot]

cherry-pick #34147 to release-5.2
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/34495

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---

What problem does this PR solve?

Issue Number: close #34148

Problem Summary:

What is changed and how it works?

1: solve the FD loss when encounter left outer join nested.
2: Introduce a new concept of condition-FD named as Cond-FD (detail see doc.go) which is more useful than lax constant and lax equiv theoretically.

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

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

planner: introduce Cond-FD to maintain null-constraint FD

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[ti-chi-bot]

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[ti-srebot]

/run-all-tests

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