fix: log eigenvalue monitor values

[he-yufeng]

Summary

• replace the nonexistent self.ev_values reference in eigenvalue monitor logging
• avoid indexing the dict_values view returned by self.block_eigenvalue.values()
• add a small regression helper/test for the event payloads

Fixes #7983.

To verify

• python -m py_compile deepspeed\runtime\engine.py tests\unit\runtime\test_engine_eigenvalue.py
• git diff --check
• AST-extracted helper smoke test: passed

I also tried python -m pytest tests\unit\runtime\test_engine_eigenvalue.py -q on this Windows checkout. Collection failed before the test body because the local package import resolves deepspeed.accelerator differently in this clone/environment. The touched code and the helper itself both compile, and the helper smoke test exercises the exact event construction without importing the full package.