grpc: place defaultStreamInterceptor after user interceptors

[easwars]

The defaultStreamInterceptor was introduced in #9226.

This change places the defaultStreamInterceptor which performs certain common logic for all non-unary RPCs to live after the user interceptors and before the xDS filters. This ensures that the work of the defaultStreamInterceptor stays invisible to the user interceptors. Specifically, it calls RecvMsg twice for non server-streaming RPCs and calls CloseSend after sending the only message for non client-streaming RPCs.

RELEASE NOTES: none

[easwars]

/gemini review

[gemini-code-assist]

Code Review

This pull request modifies the order of stream client interceptors in clientconn.go so that defaultStreamInterceptor is appended to the end of the interceptors slice rather than prepended. It also updates existing tests and adds a new end-to-end test (TestDefaultStreamInterceptor_InteractionWithXDSFilters) to verify that the internal behaviors of the default stream interceptor are not visible to user-defined interceptors and interact correctly with xDS filters. The feedback highlights several misleading comments in the new test assertions regarding client-side terminology and accumulated message counts, and suggests checking the ignored error returned by CloseSend().

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.47%. Comparing base (5c58cee) to head (ebe647c).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9404      +/-   ##
==========================================
- Coverage   87.51%   87.47%   -0.05%     
==========================================
  Files         429      430       +1     
  Lines       30643    30675      +32     
==========================================
+ Hits        26817    26832      +15     
- Misses       3826     3842      +16     
- Partials        0        1       +1     

Files with missing lines	Coverage Δ
clientconn.go	92.61% <100.00%> (+0.26%)	⬆️
stream.go	88.31% <ø> (ø)

... and 24 files with indirect coverage changes

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[easwars]

/gemini review

[gemini-code-assist]

Code Review

This pull request modifies the client connection interceptor chaining to append the defaultStreamInterceptor to the end of the interceptors slice instead of prepending it. It updates existing tests in stream_test.go to verify that the default stream interceptor's automatic CloseSend and RecvMsg behaviors are not visible to user-defined interceptors. Additionally, it introduces a new end-to-end test in test/xds/xds_client_filter_e2e_test.go to verify the interaction between the default stream interceptor and xDS filters across various RPC types, and extends the tracking filter builder in test/xds/xds_server_filter_state_retention_test.go to support client-side filter interception. There are no review comments, and I have no additional feedback to provide.