Restore: refine split code for both compacted sst files and logs (#56917)

[ti-chi-bot]

This is an automated cherry-pick of #56917

What problem does this PR solve?

Issue Number: ref #56522

This is the first PR split from #54813.

Problem Summary:
Focus on restore compacted sst files

What changed and how does it work?

This PR primarily makes the following adjustments:

1. Removal of Log Split: The log splitting logic has been removed, simplifying the code structure and making future usage more convenient.

2. Unified Split Logic: The splitting logic for SST files and log files has been unified, allowing both to share the same logic, reducing code duplication and improving maintainability.

3. Facilitates Future Extensions: This unified approach makes it easier to extend and modify the handling of SST and log files in the future, enhancing the flexibility of the code.

Overall, these changes lead to a cleaner codebase with clearer logic, laying a solid foundation for future development and maintenance.

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]

@3pointer This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[ti-chi-bot]

@ti-chi-bot: ## If you want to know how to resolve it, please read the guide in TiDB Dev Guide.

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 ti-community-infra/tichi repository.

[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 3pointer, benjamin2037 for approval. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

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

Needs approval from an approver in each of these files:

• br/OWNERS
• pkg/lightning/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/check_dev_2	4eb8bab	link	true	/test check-dev2
idc-jenkins-ci-tidb/build	4eb8bab	link	true	/test build
idc-jenkins-ci-tidb/unit-test	4eb8bab	link	true	/test unit-test
idc-jenkins-ci-tidb/mysql-test	4eb8bab	link	true	/test mysql-test
pull-br-integration-test	4eb8bab	link	true	/test pull-br-integration-test
idc-jenkins-ci-tidb/check_dev	4eb8bab	link	true	/test check-dev

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-sigs/prow repository. I understand the commands that are listed here.