api: sync API V3 keyspace identity protos

[disksing]

Summary

• Reset the PR branch onto release-8.5-keyspace@20fe3db22397921ca101510bdef2dcee094134a4.
• Port the applicable API V3 protocol changes from add API V3 keyspace identity protos pingcap/kvproto#1458 (7022f46937bc35125fb6d65aad5a0eedd59e7cfd).
• Cherry-pick the namespace service split from keyspacepb: split namespace service pingcap/kvproto#1505 (7932dbe6f8bd06031c265abf93406e2bb917781f).
• Regenerate Go bindings and scripts/proto.lock with the downstream release toolchain.
• Track SYS-134.

Downstream differences

• Keep the release-line schema and file formatting instead of importing unrelated changes from upstream master.
• Keep the Resource Manager protocol and generated bindings unchanged from release-8.5-keyspace.
• externalworkloadpb, keyspace_encryptionpb, DfsStatScope, and the newer GC KeyspaceScope are absent from this release line, so their upstream-only edits are not reintroduced.
• For #1505, retain only the Namespace service split and regenerate against the release-line schema; the pdpb comment from that upstream commit was already present from the #1458 port.

Validation

• make check
• GOPROXY=https://goproxy.cn,direct GOSUMDB=off go test ./...
• Re-ran scripts/generate_go.sh; generated output had zero drift.
• go mod tidy completed with no go.mod or go.sum changes.
• git diff --check
• Reviewed all new proto indentation against each target-base file style.
• Verified proto/resource_manager.proto, pkg/resource_manager/resource_manager.pb.go, and the Resource Manager lock definition have zero diff from the target base.

Traceability

• Upstream API V3 PR: add API V3 keyspace identity protos pingcap/kvproto#1458
• Upstream API V3 merge commit: 7022f46937bc35125fb6d65aad5a0eedd59e7cfd
• Upstream namespace service PR: keyspacepb: split namespace service pingcap/kvproto#1505
• Upstream namespace service merge commit: 059694ae4472276644613acccefa24cbc89d959f
• Upstream namespace service implementation commit: 7932dbe6f8bd06031c265abf93406e2bb917781f
• Downstream head: f34368224b8e021fc56c2d4fe94ea34130284316

[pingcap-cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 11 committers have signed the CLA.

✅ rleungx
✅ disksing
❌ glorv
❌ JmPotato
❌ ekexium
❌ tiancaiamao
❌ wshwsh12
❌ lcwangchao
❌ hbisheng
❌ MyonKeminta
❌ you06
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