planner: move fields from ast.Prepared to planner.PlanCacheStmt (#52373)

[ti-chi-bot]

This is an automated cherry-pick of #52373

What problem does this PR solve?

Issue Number: ref #51407

Problem Summary: planner: move fields from ast.Prepared to planner.PlanCacheStmt

What changed and how does it work?

NO LOGICAL CHANGE, ONLY REFACTOR

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

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign time-and-fate for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

@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/unit-test	fee09c4	link	true	/test unit-test
idc-jenkins-ci-tidb/build	fee09c4	link	true	/test build
idc-jenkins-ci-tidb/check_dev_2	fee09c4	link	true	/test check-dev2
idc-jenkins-ci-tidb/check_dev	fee09c4	link	true	/test check-dev
idc-jenkins-ci-tidb/mysql-test	fee09c4	link	true	/test mysql-test

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.