proto: backport FTS/TiCI protocols to release-8.5-fts

[AilinKid]

Summary

Backport the existing FTS/TiCI protocol stack to feature/release-8.5-fts for pingcap/tidb#71280.

Cherry-pick the five previously adapted commits from cp-fts-858-kvproto (47bcf5dc38ad): #1319, #1332, #1356, #1457 and #1432. They add shard metadata, versioned ranges and services, estimate-count RPCs, and MPP shard dispatch. Each commit retains its cherry-pick provenance.

The target starts at ab2787838a97; retain its #1524 resource-usage change. The resulting tree differs from the old FTS branch only by that target change. No backup metadata schema changes.

Validation

• go test -mod=readonly ./pkg/... passed (generated Go packages compile; most have no tests).
• Patch integrity and exact source/target delta checks passed.
• Rust/C++ builds and live TiCI integration were not run.

Summary by CodeRabbit

• New Features
  • Added version-aware point-range lookups, allowing requests to specify the read timestamp for each range.
  • Added TiCI full-text search shard information to coprocessor and MPP requests, including shard retry details.
  • Added an API for estimating TiCI full-text search result counts.
  • Added a versioned coprocessor service for processing timestamp-aware requests.
  • Versioned lookup requests require point ranges and must not include standard range specifications.

[ti-chi-bot]

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 74d720e6-2709-49a1-a3da-a2aa99026fc8

📥 Commits

Reviewing files that changed from the base of the PR and between ab27878 and d7957dc.

⛔ Files ignored due to path filters (4)

• pkg/coprocessor/coprocessor.pb.go is excluded by !**/*.pb.go
• pkg/mpp/mpp.pb.go is excluded by !**/*.pb.go
• pkg/tikvpb/tikvpb.pb.go is excluded by !**/*.pb.go
• scripts/proto.lock is excluded by !**/*.lock

📒 Files selected for processing (3)

• proto/coprocessor.proto
• proto/mpp.proto
• proto/tikvpb.proto

Included review availability: Your plan provides up to 2 included reviews per hour; 1 remains after this review.

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📝 Walkthrough

Walkthrough

The protobuf contracts add versioned point-range lookups, TiCI shard metadata, estimate-count messages, MPP routing data, and two RPC endpoints.

Changes

TiCI protocol extensions

Layer / File(s)	Summary
Versioned lookup contracts proto/coprocessor.proto	Adds VersionedKeyRange and versioned-range fields to Request and StoreBatchTask. The fields require point ranges.
Shard metadata and estimate contracts proto/coprocessor.proto, proto/mpp.proto	Adds shard metadata, TiCI estimate-count messages, batch retry shard data, and MPP table shard information.
TiCI RPC endpoints proto/tikvpb.proto	Adds GetEstimateTiCICount to Tikv and adds the VersionedKv.VersionedCoprocessor service. The latter documents the versioned-range request invariant.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to d7957

The protocol additions have no identified merge-blocking risk.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: backporting the FTS/TiCI protocol additions to the release-8.5-fts branch.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

Some tools did not complete. Review the errors below.

🔧 Buf (1.72.0)

proto/coprocessor.proto

fatal: unable to access 'https://github.com/pingcap/kvproto.git/': Failed to connect to github.com:443 over proxy 127.0.0.1 after 0 ms: Could not connect to server
fatal: could not fetch d0f83a0dabdfe96285e9aaf7b0006ff64590e4f6 from promisor remote

proto/mpp.proto

fatal: unable to access 'https://github.com/pingcap/kvproto.git/': Failed to connect to github.com:443 over proxy 127.0.0.1 after 0 ms: Could not connect to server
fatal: could not fetch d0f83a0dabdfe96285e9aaf7b0006ff64590e4f6 from promisor remote

proto/tikvpb.proto

fatal: unable to access 'https://github.com/pingcap/kvproto.git/': Failed to connect to github.com:443 over proxy 127.0.0.1 after 0 ms: Could not connect to server
fatal: could not fetch d0f83a0dabdfe96285e9aaf7b0006ff64590e4f6 from promisor remote

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_{A rabbit carries ranges bright,
With read timestamps tucked in tight.
Shards join the routing trail,
Count estimates cross the rail,
New RPC paths complete the flight.}

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