[CI] Add four unittest

[Echo-Nie]

Motivation

Enhance code reliability by adding unit tests for critical modules, ensuring consistent behavior and catching regressions early.

Modifications

Added unit tests for:

• tests/engine/test_kv_cache_interface.py
• tests/layers/test_moba_attention_backend.py
• tests/output/test_pooler.py
• tests/output/test_stream_transfer_data.py

Usage or Command

python tests/engine/test_kv_cache_interface.py
...

Accuracy Tests

Name	Stmts	Miss	Cover
moba_attention_backend.py	64	3	95%
stream_transfer_data.py	18	0	100%
pooler.py	29	0	100%
kv_cache_interface.py	17	0	100%

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[Echo-Nie]

/re-run all-failed

[EmmonsCurse]

LGTM