Implement RFC 7047 JSON-RPC Client for OVSDB

[ljluestc]

PR: Implement RFC 7047 JSON-RPC Client for OVSDB

What this PR does / why we need it:

This PR introduces a native pure-Go JSON-RPC client for OVSDB in vendor/yunion.io/x/ovsdb/client. This implementation adheres to RFC 7047 and allows the application to interact directly with OVN Northbound/Southbound databases without relying on external ovn-nbctl processes. This improves performance, transaction atomicity, and enables real-time state synchronization via OVSDB monitoring.

Key Changes:

• Native Client: Implemented Client (client.go, rpc.go) which manages persistent TCP/Unix connections and handles the JSON-RPC 1.0 request/response lifecycle, including async notifications.
• Monitoring: Added MonitorDB (monitor.go) which leverages reflection to map OVSDB table updates directly into the generated Go structs found in yunion.io/x/ovsdb/schema/ovn_nb. This allows for maintaining an automatic, real-time in-memory cache of the database.
• Transactions: Implemented TransactOps (transact.go) to support atomic operations (Insert, Update, Delete, Mutate) with automatic, schema-aware serialization of Go structs to OVSDB JSON format.
• Build Fix: Manually registered the new package in vendor/modules.txt to resolve build issues in the vendored environment.
• Verification: Added a CLI tool cmd/ovsdb-check to verify connection establishment, monitoring synchronization, and transaction execution.

• Smoke testing completed
• Unit test written (Validation tool added in cmd/ovsdb-check)