PR1: Infrastructure — Add nacos-sdk-proto/go, PayloadCodec, CI rewrite, module path v3

[cxhello]

Parent issue: #879

Scope

This is the first PR in the v3 roadmap. It lays the foundation for all subsequent PRs.

Changes

1. Module path v2 → v3, CLIENT_VERSION → Nacos-Go-Client:v3.0.0
2. Add dependency github.com/nacos-group/nacos-sdk-proto/go v1.0.0-beta.8
3. Implement PayloadCodec — centralized message type registry + protojson encode/decode, covering all 5 modules (common/config/naming/lock/ai, 73 message types)
4. Upgrade dependencies — Go 1.21→1.22, grpc v1.67.3→v1.71.2, protobuf v1.36.5→v1.36.4
5. Remove outdated dependency — alibaba-cloud-sdk-go v1 direct import removed, migrated KMS code to alibabacloud-dkms-gcs-go-sdk (移除那些过时的依赖比如github.com/aliyun/alibaba-cloud-sdk-go #871)
6. Rewrite CI — 4-job pipeline: lint / unit-test (Go 1.22-1.24 matrix) / integration-grpc (Nacos 3.x Docker) / integration-nacos2 (Nacos 2.x Docker)

Dependency versions

Dependency	Old (v2)	New (v3)
Go	1.21	1.22
nacos-sdk-proto/go	—	v1.0.0-beta.8
google.golang.org/grpc	v1.67.3	v1.71.2
google.golang.org/protobuf	v1.36.5	v1.36.4
alibaba-cloud-sdk-go	v1.61.1800 (direct)	indirect only

New files

• common/remote/codec/payload_codec.go
• common/remote/codec/payload_codec_test.go
• .github/workflows/ci.yml

Non-goals

• Wiring PayloadCodec into existing gRPC layer (PR2)
• Deleting old rpc_request/ and rpc_response/ packages (PR2)
• Auth/Naming/Config bug fixes (PR3-5)

Known issues

• alibaba-cloud-sdk-go remains as indirect dependency (pulled by aliyun-secretsmanager-client-go)
• KMS dedicated encryption has a breaking change in ciphertext encoding format (v3 major version bump)

Related

• Fixes 移除那些过时的依赖比如github.com/aliyun/alibaba-cloud-sdk-go #871
• Part of [Proposal] nacos-sdk-go v3: Adopt nacos-sdk-proto + gRPC Layer Refactor #879