tikvrpc: add default request origin (#1975)

[ti-chi-bot]

This is an automated cherry-pick of #1975

What changed

• Add a process-wide default request origin in tikvrpc.
• Fill kvrpcpb.Context.request_origin from that default when creating or attaching request context.
• Keep the default as unspecified so non-TiDB client-go users do not get TiDB trust by accident.

Dependency stack

• Uses merged kvrpcpb: add request origin to context pingcap/kvproto#1479 for RequestOrigin and Context.request_origin.
• Ref Make TiKV identify TiDB requests and strengthen TS checks for non-TiDB requests pingcap/tidb#68799.
• No temporary kvproto replace remains; the root module, integration test module, and example modules are bumped directly to the merged kvproto pseudo-version.

Tests

• gotestsum --format short-verbose -- ./tikvrpc
• go test ./tikvrpc -run '^TestDefaultRequestOrigin$' -race
• cd integration_tests && go list -mod=readonly ./...
• for mod in $(find examples -name go.mod -print | sort); do (cd "${mod%/go.mod}" && go list -mod=readonly ./...); done
• git diff --check

Summary by CodeRabbit

• New Features

  • Configurable default request origin for RPCs, ensuring consistent request identification and tracking across operations.

• Chores

  • Bumped an indirect dependency used by examples and integration tests to a newer commit across multiple modules.

• Tests

  • Added unit tests to verify default request origin behavior and that explicit origins are preserved across RPC creation and attachment.

[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 brson 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.

Details

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]

@ekexium 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.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 98a3fc89-a23a-4aca-812e-042baec1472e

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}