planner: regard NULL as point when accessing composite index (#30244)

[qw4990]

cherry-pick #30244 #29999 #30340, no conflict

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What problem does this PR solve?

Issue Number: close #29650

Problem Summary: planner: regard NULL as point when accessing composite index

What is changed and how it works?

planner: regard NULL as point when accessing composite index

Check List

Tests

• Unit test

Release note

planner: regard NULL as point when accessing composite index

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Reminiscent
• Yisaer

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[ti-chi-bot]

@qw4990: 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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[qw4990]

/run-all-tests