support bypassing shared lock

[you06]

What problem does this PR solve?

Issue Number: ref tikv/tikv#19087

Problem Summary:

What is changed and how it works?

This PR support parsing the TiKV's shared lock and bypass them in conflict check.

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

Summary by CodeRabbit

Release Notes

• New Features

  • Added support for shared locks in the KVStore layer, enhancing concurrent transaction management and lock isolation capabilities.

• Tests

  • Expanded test coverage to validate detection and handling of the new shared lock type.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[coderabbitai]

📝 Walkthrough

Walkthrough

This change adds support for a new "Shared" lock type to the TiKV storage layer. It introduces a new Shared = 'H' enumerator to the LockType enum, updates lock decoding and retrieval logic to handle the new type, adds test coverage, and updates the kvproto submodule reference.

Changes

Cohort / File(s)	Summary
Lock Type Definition dbms/src/Storages/KVStore/TiKVHelpers/TiKVRecordFormat.h	Added new enumerator Shared = 'H' to the LockType enum in the DB::RecordKVFormat namespace
Lock Handling Logic dbms/src/Storages/KVStore/TiKVHelpers/DecodedLockCFValue.cpp	Updated decodeLockCfValue to recognize and early-return for SharedLock; broadened Inner::getLockInfoPtr early-return condition to treat SharedLock same as Lock and PessimisticLock (returns nullptr)
Test Coverage dbms/src/Storages/KVStore/tests/gtest_kvstore.cpp	Added test block in RegionKVStoreOldTest::RegionReadWrite that inserts a SharedLock entry, creates a committed scanner, and verifies lock info returns nullptr
Submodule Reference contrib/kvproto	Updated kvproto submodule reference from commit db74bf0 to commit 6db24b6

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A SharedLock hops into the fray,
New enum value joins the play,
'H' marks it in the KV store,
Decoded swift, returns as before,
Tests confirm it's working right! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'support bypassing shared lock' accurately reflects the main objective of the PR, which adds support for parsing and bypassing TiKV's shared locks in conflict checks.
Description check	✅ Passed	The PR description follows the required template with all main sections completed: problem statement, changes explained, tests checked (unit test), side effects assessed, and release note provided.

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✨ Finishing touches

• 📝 Generate docstrings

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[ti-chi-bot]

[FORMAT CHECKER NOTIFICATION]

Notice: To remove the do-not-merge/needs-linked-issue label, please provide the linked issue number on one line in the PR body, for example: Issue Number: close #123 or Issue Number: ref #456.

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