[CI]【Hackathon 9th Sprint No.51】NO.51 功能模块 fastdeploy/scheduler/dp_scheduler.py 单测补充 (#5046)

* update test utils

* Add comprehensive unit tests for DP scheduler functionality

- Add test_dp_scheduler.py with full-featured unit tests supporting both normal and standalone modes
- Add test_dp_scheduler_simple.py with lightweight mock-based tests for easy execution
- Add comprehensive README.md documenting test architecture and usage
- Tests cover DPLocalScheduler and DPScheduler classes with focus on:
  - Request lifecycle management and TTL support
  - Response handling and routing
  - Resource-based scheduling and constraint handling
  - Multi-threading and concurrent operations
  - Splitwise role support (prefill vs decode)
  - Error handling and edge cases
  - Thread-safe operations with proper synchronization

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Co-Authored-By: Claude <noreply@anthropic.com>

* Remove tests/multimodal/test_utils.py

This file appears to be duplicate or misplaced, removing it to clean up the test structure.

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Co-Authored-By: Claude <noreply@anthropic.com>

* update

* fix

* rm unused file

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Co-authored-by: Claude <noreply@anthropic.com>

Author: essos-bot