planner: let scope only be affected when check FDs

[winoros]

What problem does this PR solve?

What is changed and how it works?

Check List

Tests

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

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to update the tidb-ansible repository
• Need to be included in the release note

[AilinKid]

got, the new built equal condition for #column5 (projected from correlated) and #column4 (extracted from correlated's column) can't resolve it's index in physical optimization, cause this EQ func can't find #column4 from it's both child's schema

[AilinKid]

LGTM