resourcecontrol, tikvrpc: backport RC paging pre-charge hint

[JmPotato]

Problem

Backport the client-go transport required by the merged tikv/pd#11003 so TiDB can provide a predicted read-bytes hint for request-side resource-control pre-charge on release-nextgen-202603.

Changes

• Consume the PD client from the release-nextgen-202603 merge of client/resource_group: backport RC pre-charge and runtime state pd#11003 (v0.0.0-20260716095117-1636e69a936b).
• Add tikvrpc.Request.PredictedReadBytes and expose the hint through resource-control RequestInfo.
• Classify coprocessor requests so PD only applies paging pre-charge to eligible read requests.
• Keep the release branch's Go toolchain and PD GC, MetaStorage, and keyspace client APIs unchanged.

The hint is internal to client-go and does not change the TiKV wire protocol. A zero hint preserves the existing settlement-only behavior.

Dependencies and source

• Consumes the merged release-branch PD client from client/resource_group: backport RC pre-charge and runtime state pd#11003.
• Backports resourcecontrol, tikvrpc: add PredictedReadBytes hint for RC paging pre-charge #1947.
• Related issues: client/resource_group: add RC paging pre-charge controller consuming client-supplied read-bytes hint pd#10612 and coprocessor: add RC paging pre-charge read-bytes prediction (EMA + hint emission) pingcap/tidb#68085.

Tests

go test --tags=intest ./...
(cd integration_tests && go test ./... -run '^$' -count=0)
git diff --check upstream/release-nextgen-202603...HEAD

Known CI results:

• GitHub Actions integration-tikv failed in the timing-sensitive TestSnapshotFail/TestRetryPointGetResolveTS, outside the changed resource-control paths. A job-only rerun requires maintainer permission.
• Prow pull-integration-test-release-nextgen fails because the release branch lacks the TiDB-like key encoding test fix from tests: use TiDB-like keys in next-gen integration tests #2010 (00f57d88370fa62fb83e895f05a73fabb499904e). That fix should be backported separately rather than mixed into this feature backport.

Compatibility

No wire-protocol change. Existing callers that do not set PredictedReadBytes retain the previous behavior. The backport intentionally keeps the release branch's existing PD client APIs and dependency baseline.

None

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[JmPotato]

/retest

[ti-chi-bot]

@YuhaoZhang00: adding LGTM is restricted to approvers and reviewers in OWNERS files.

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[YuhaoZhang00]

/retest

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@JmPotato: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-integration-test-release-nextgen	b5a120c	link	false	/test pull-integration-test-release-nextgen

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, rleungx, YuhaoZhang00

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• OWNERS [cfzjywxk]
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-07-16 12:21:02.946831888 +0000 UTC m=+889048.982926943: ☑️ agreed by cfzjywxk.
• 2026-07-16 13:17:47.432724613 +0000 UTC m=+892453.468819659: ☑️ agreed by rleungx.