Feat: add some dubbo config and use new config style

[Similarityoung]

What this PR does:

This pull request significantly refactors and extends the Dubbo client configuration and integration logic to support more flexible and feature-rich Dubbo proxying. The main changes include expanding the DubboProxyConfig struct with new fields and helpers, updating the Dubbo client creation to use the latest dubbo-go v3.3.1 client API, and adding comprehensive unit tests for the new configuration options.

Key changes:

DubboProxyConfig Enhancements

• Added new fields to DubboProxyConfig for advanced Dubbo features: Cluster, Check, Protocol, Filter, Serialization, Sticky, and Params, each with documentation and sensible defaulting logic. Helper methods (GetCluster, GetProtocol, GetCheck) were introduced to provide default values and maintain backward compatibility.

Dubbo Client Refactor

• Switched Dubbo client initialization from the old dg.RootConfig approach to the new dclient.NewClient API, updating the registry and application configuration handling to use global.RegistryConfig and global.ApplicationConfig. [1] [2] [3] [4]
• Refactored the service reference creation logic to use a new buildReferenceOptions method, which builds the reference configuration using the new API and applies all advanced options from DubboProxyConfig and the integration request. This enables support for all new configuration fields and ensures correct option precedence.

Testing

• Added comprehensive unit tests in config_test.go to verify the new configuration fields and helper methods, including edge cases for defaulting and explicit configuration.

Which issue(s) this PR fixes:

Fixes #631

[sonarqubecloud]

Quality Gate passed

Issues
9 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

❌ Patch coverage is 10.62500% with 143 lines in your changes missing coverage. Please review.
✅ Project coverage is 20.55%. Comparing base (5ac9162) to head (9f8593d).

Files with missing lines	Patch %	Lines
pkg/client/dubbo/dubbo.go	4.66%	142 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #862      +/-   ##
===========================================
- Coverage    20.63%   20.55%   -0.09%     
===========================================
  Files          259      260       +1     
  Lines        19017    19143     +126     
===========================================
+ Hits          3925     3935      +10     
- Misses       14707    14822     +115     
- Partials       385      386       +1     

Flag	Coverage Δ
unittests	20.55% <10.62%> (-0.09%)	⬇️

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