planner, statistics: fix the inconsistent est when table has no stats (#52427)

[ti-chi-bot]

This is an automated cherry-pick of #52427

What problem does this PR solve?

Issue Number: close #52426

Problem Summary:

What changed and how does it work?

The Selectivity needs a memory obj to trigger the pseudo estimation.

We add one.

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

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-8.1@e19f78c). Click here to learn what that means.
The diff coverage is 90.2439%.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.1     #52614   +/-   ##
================================================
  Coverage               ?   72.2664%           
================================================
  Files                  ?       1467           
  Lines                  ?     426880           
  Branches               ?          0           
================================================
  Hits                   ?     308491           
  Misses                 ?      99082           
  Partials               ?      19307           

Flag	Coverage Δ
unit	71.1338% <90.2439%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	53.9957% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	41.0929% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, winoros

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-04-15 12:15:37.003541876 +0000 UTC m=+253956.114588326: ☑️ agreed by hawkingrei.
• 2024-04-15 13:47:18.477106515 +0000 UTC m=+259457.588152956: ☑️ agreed by winoros.