planner: correctly set StatsVersion of tablePlan in copTask

[xuyifangreeneyes]

What problem does this PR solve?

Issue Number: close #27083

Problem Summary:
Explain results show stats:pseudo in operator info though it uses true stats.

What is changed and how it works?

When copTask.tablePlan is first created, we set its stats as empty StatsInfo with correct StatsVersion. We don't set StatsInfo directly because it depends on copTask.indexPlan and copTask.indexPlan may change later. In (*copTask).finishIndexPlan, when we assign copTask.indexPlan's stats to copTask.tablePlan, we keep StatsVersion unchanged.

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:

• Reminiscent
• winoros

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[xuyifangreeneyes]

/cc @winoros

[xuyifangreeneyes]

/cc @Reminiscent @time-and-fate

[Reminiscent]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 86c6e9a

[xuyifangreeneyes]

/run-all-tests

[xuyifangreeneyes]

/run-all-tests

[winoros]

/merge

[winoros]

/merge