fix(core): resolve #3247 lock misuse and map exposure races

[xxs588]

Description

Fixes #3247

This PR addresses core race points outside common/extension with minimal scoped changes:

• dubbo.go
  • SetProviderService now uses proLock (instead of conLock)
  • GetConsumerConnection now uses conLock.RLock/RUnlock
• cluster/router/chain/chain.go
  • RouterChain.Route now snapshots invokers under RLock before iteration
• config/service.go
  • GetProviderServiceMap and GetConsumerServiceMap now return copied maps instead of internal references

Local verification:

• go test -race ./cluster/router/chain/... ./config/...
• go test -race ./... (shows pre-existing race failures in unrelated existing packages such as cluster/cluster/failback, config_center/apollo, config_center/file)

Checklist

• I confirm the target branch is develop
• Code has passed local testing
• I have added tests that prove my fix is effective or that my feature works

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.25%. Comparing base (60d1c2a) to head (1c6a61d).
⚠️ Report is 757 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3265      +/-   ##
===========================================
+ Coverage    46.76%   48.25%   +1.48%     
===========================================
  Files          295      466     +171     
  Lines        17172    34058   +16886     
===========================================
+ Hits          8031    16433    +8402     
- Misses        8287    16294    +8007     
- Partials       854     1331     +477     

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[sonarqubecloud]

Quality Gate passed

Issues
0 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

[Alanxtl]

lgtm