[3.3] Optimize TriRpcStatus by adding http status code to its description

[zrlw]

What is the purpose of the change?

When the provider which try to enable servlet for triple at springboot3 but it doesn't import dubbo-spring-boot-3-autoconfigure into its pom.xml, the consumer will encounter RpcException like this,

2025-09-24T19:41:50.862+08:00 ERROR 25776 --- [dubbo-spring-consumer] [io-60052-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: org.apache.dubbo.rpc.RpcException: java.util.concurrent.ExecutionException: org.apache.dubbo.rpc.StatusRpcException: UNIMPLEMENTED : invalid content-type: application/json]

however, UNIMPLEMENTED : invalid content-type: application/json is inaccurate, it might be better to say UNIMPLEMENTED : HTTP status 404, content-type: application/json.

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 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.02%. Comparing base (2170f0f) to head (6ac7c3c).

Files with missing lines	Patch %	Lines
...c/main/java/org/apache/dubbo/rpc/TriRpcStatus.java	0.00%	1 Missing ⚠️
...rotocol/tri/stream/AbstractTripleClientStream.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #15708      +/-   ##
============================================
- Coverage     61.05%   61.02%   -0.03%     
+ Complexity    11704    11696       -8     
============================================
  Files          1923     1923              
  Lines         87081    87081              
  Branches      13115    13115              
============================================
- Hits          53165    53141      -24     
- Misses        28479    28486       +7     
- Partials       5437     5454      +17     

Flag	Coverage Δ
integration-tests-java21	32.84% <0.00%> (-0.14%)	⬇️
integration-tests-java8	32.99% <0.00%> (+0.05%)	⬆️
samples-tests-java21	32.66% <0.00%> (-0.02%)	⬇️
samples-tests-java8	30.38% <0.00%> (+0.03%)	⬆️
unit-tests-java11	58.99% <0.00%> (-0.02%)	⬇️
unit-tests-java17	58.76% <0.00%> (+<0.01%)	⬆️
unit-tests-java21	58.75% <0.00%> (-0.01%)	⬇️
unit-tests-java8	58.99% <0.00%> (+<0.01%)	⬆️

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[EarthChen]

LGTM

[finefuture]

LGTM.

[EarthChen]

LGTM