Support custom registry ip and port for Nacos registration

[somiljain2006]

• I have read the CONTRIBUTING.md guidelines.
• I have registered the PR changes.

Ⅰ. Describe what this PR did

• Add support for registry.nacos.ip and registry.nacos.port
• Allow overriding the address registered to Nacos independently of the server listen address
• Prioritize System properties over file configuration, with fallback to default behavior
• Ensure backward compatibility when no override is configured

Ⅱ. Does this pull request fix one issue?

Fixes #8016

Ⅲ. Why don't you add test cases (unit test/integration test)?

• Added comprehensive tests for override and precedence scenarios

Ⅳ. Describe how to verify it

1. Run unit tests:
   ./mvnw -pl discovery/seata-discovery-nacos -Dtest=NacosRegistryServiceImplTest test

2. Start the Nacos server locally

3. Run Seata server from source with JVM overrides:
   ./mvnw -pl server clean compile exec:java
   -Dexec.mainClass="org.apache.seata.server.ServerApplication"
   -Dregistry.nacos.ip=127.0.0.1
   -Dregistry.nacos.port=21908

4. Verify registration in Nacos:
   curl http://localhost:8848/nacos/v1/ns/instance/list?serviceName=seata-server

Expected result:

• IP = 127.0.0.1
• Port = 21908

This confirms that System properties override the default registration address.

Ⅴ. Special notes for reviews

N/A

[codecov]

Codecov Report

❌ Patch coverage is 83.87097% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.30%. Comparing base (49e99de) to head (3927e70).
⚠️ Report is 27 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...overy/registry/nacos/NacosRegistryServiceImpl.java	83.87%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #8026      +/-   ##
============================================
+ Coverage     72.23%   72.30%   +0.07%     
  Complexity      876      876              
============================================
  Files          1310     1310              
  Lines         49975    50002      +27     
  Branches       5945     5951       +6     
============================================
+ Hits          36099    36154      +55     
+ Misses        10924    10896      -28     
  Partials       2952     2952              

Files with missing lines	Coverage Δ
...overy/registry/nacos/NacosRegistryServiceImpl.java	75.67% <83.87%> (+0.80%)	⬆️

... and 9 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[somiljain2006]

@funky-eyes Can you review this pr?

[somiljain2006]

I reproduced the CI failures locally using the same full test command.

The failing tests are:

org.apache.seata.config.nacos.NacosMockTest
io.seata.config.extend.TestConfigFromExtendSPI

The failures occur in seata-config-nacos, while my change only affects seata-discovery-nacos.

I also verified that isolated module tests pass locally:

./mvnw -pl config/seata-config-nacos -DskipITs test

The NacosMockTest failure appears to be timing/startup related:

com.alibaba.nacos.api.exception.NacosException:
Client not connected, current status:STARTING

So this currently looks like an unrelated flaky/full-suite integration issue rather than a regression introduced by the registry IP/port customization change.