feat: add verbose flag to DeviceStatsMonitor for non-expert mode

[deependujha]

What does this PR do?

Fixes #18652

DeviceStatsMonitor previously dumped all device stats unconditionally, overwhelming beginner users unfamiliar with PyTorch allocator internals.

Added a verbose flag (default True to preserve existing behavior).
When verbose=False, only core metrics are logged: memory usage and CPU utilization for CUDA/CPU, and HBM memory metrics for TPU.

Changes:

• Added _CORE_DEVICE_STATS_KEYS and _CORE_TPU_STATS_PREFIXES module-level constants
• Added _filter_core_device_stats static method to DeviceStatsMonitor
• Added verbose parameter to __init__ with updated docstring
• Added parametrized tests for both CPU and GPU

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• Did you make sure to update the documentation with your changes? (if necessary)
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• Did you verify new and existing tests pass locally with your changes?
• Did you list all the breaking changes introduced by this pull request?
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📚 Documentation preview 📚: https://pytorch-lightning--21706.org.readthedocs.build/en/21706/

[Copilot]

Pull request overview

Adds a verbose flag to DeviceStatsMonitor to support a “non-expert” logging mode that reduces the amount of device statistics emitted to loggers, addressing issue #18652.

Changes:

• Added a verbose parameter to DeviceStatsMonitor (default True) and core-metric filtering logic for verbose=False.
• Introduced module-level constants defining the “core” metrics and a helper to filter stats dictionaries.
• Added parameterized tests covering verbose=True/False behavior for CPU and CUDA.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/lightning/pytorch/callbacks/device_stats_monitor.py	Adds verbose flag and core-metric filtering for device stats logging.
tests/tests_pytorch/callbacks/test_device_stats_monitor.py	Adds new parameterized tests validating verbose vs non-verbose logging on CPU and CUDA.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79%. Comparing base (78bf021) to head (ea6eb4d).
✅ All tests successful. No failed tests found.
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HEAD has 1297 uploads less than BASE

Flag	BASE (78bf021)	HEAD (ea6eb4d)
cpu	335	42
python	23	3
lightning_fabric	108	0
pytest	168	0
python3.12	96	12
python3.10	24	3
lightning	120	15
python3.13	72	9
python3.11	48	6
python3.12.7	72	9
pytorch2.4.1	12	3
pytest-full	167	42
pytorch2.8	24	6
pytorch_lightning	107	27
pytorch2.6	12	3
pytorch2.5.1	12	3
pytorch2.1	23	6
pytorch2.3	12	3
pytorch2.2.2	12	3
pytorch2.9	24	6
pytorch2.10	24	6
pytorch2.7	12	3

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #21706     +/-   ##
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- Coverage      87%      79%     -8%     
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  Files         270      267      -3     
  Lines       23973    23922     -51     
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- Hits        20748    18809   -1939     
- Misses       3225     5113   +1888