planner: set min for high risk plan steps (#56631)

[ti-chi-bot]

This is an automated cherry-pick of #56631

What problem does this PR solve?

Issue Number: close #55126

Problem Summary:

What changed and how does it work?

Ensure a minimum number of rows and a minimum row size for each plan operation for the optimizer cost model. And ensure that non-index based operations have a minimum of 1 row processed, and row length of at least 2. Index based operations can be fractional (less than 1) due to index probes being averaged out across all outer to inner probes for joins - thus the minimum of 1 row does not apply to index operations due to risk of biasing away from index joins or index merges.

Estimates at zero or below zero are possible in many situations due to realtime insert/update/delete tracking for statistics processing is not transactional (loss of statistics are OK - since it is not user data, and will be corrected next ANALYE). Below zero is rare but possible. In cardinality estimation, zero or near zero it possible due to assumption of independence with multiple predicates or multiple joins, and also with underestimation of any (or many) individual predicate(s).

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

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@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/build	74f89d8	link	true	/test build
idc-jenkins-ci-tidb/unit-test	74f89d8	link	true	/test unit-test
idc-jenkins-ci-tidb/check_dev_2	74f89d8	link	true	/test check-dev2
idc-jenkins-ci-tidb/check_dev	74f89d8	link	true	/test check-dev
idc-jenkins-ci-tidb/mysql-test	74f89d8	link	true	/test mysql-test

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