fix(registry): restore invoker URL de-duplication and keep #16108 protocol-matching fix

[onceMisery]

What is the purpose of the change?

This PR fixes a regression introduced while addressing #16108.

Background

During the #16108 fix, URL de-duplication in ServiceDiscoveryRegistryDirectory#refreshInvoker() was accidentally removed.
If registry sends duplicated instance URLs in one notification batch, toInvokers() may call protocol.refer() multiple times for the same endpoint before map finalization. The later put() overwrites earlier entries in newUrlInvokerMap, which can leave previously created invokers untracked and not destroyed.

This regresses the behavior fixed by commit a35af2742a (Remove duplicated invokers in registry notification).

What is changed

1. Restore invoker URL de-duplication in refreshInvoker()

• Re-introduce invokerUrls.stream().distinct() before toInvokers().
• Keep duplicate-notification log with original vs distinct size.

2. Keep [Bug] SpringCloudServiceInstanceNotificationCustomizer causes "Unsupported protocol" error when Spring Cloud and Dubbo services coexist on the same Nacos namespace #16108 logic correction

• Spring Cloud instance matching now requires consumer protocol to be explicitly rest.
• Avoid matching Spring Cloud instances when consumer protocol is null or non-REST.

3. Add regression test coverage

• SpringCloudServiceInstanceNotificationCustomizerTest verifies protocol-match behavior and mixed-instance handling.
• ServiceDiscoveryRegistryDirectoryTest verifies duplicated URLs in one notify batch are de-duplicated and do not trigger repeated refer flow.

Why this is needed

• Prevents duplicate refer calls and potential invoker leak in duplicate-notification scenarios.
• Preserves the intended [Bug] SpringCloudServiceInstanceNotificationCustomizer causes "Unsupported protocol" error when Spring Cloud and Dubbo services coexist on the same Nacos namespace #16108 behavior without regressing prior duplicate-notification safety.
• Adds tests to prevent future regressions.

GitHub Issue

• Fixes/relates to: #16108

Checklist

• Make sure there is a GitHub_issue field for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Make sure gitHub actions can pass. Why the workflow is failing and how to fix it?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 36.23%. Comparing base (492f78e) to head (d0a7a16).

Files with missing lines	Patch %	Lines
...stry/client/ServiceDiscoveryRegistryDirectory.java	0.00%	11 Missing ⚠️
...ingCloudServiceInstanceNotificationCustomizer.java	0.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (492f78e) and HEAD (d0a7a16). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (492f78e)	HEAD (d0a7a16)
integration-tests	1	0

Additional details and impacted files

@@             Coverage Diff              @@
##                3.2   #16133      +/-   ##
============================================
- Coverage     41.27%   36.23%   -5.04%     
+ Complexity    10492     9180    -1312     
============================================
  Files          1652     1652              
  Lines         71492    71497       +5     
  Branches      10175    10178       +3     
============================================
- Hits          29508    25907    -3601     
- Misses        37847    41658    +3811     
+ Partials       4137     3932     -205     

Flag	Coverage Δ
integration-tests	?
samples-tests	36.23% <0.00%> (-0.09%)	⬇️

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