perf: optimize training loop

[caic99]

Improvements to the training process:

• deepmd/pt/train/training.py: Added a check to skip setting the model to training mode if it already is. The profiling result shows it takes some time to recursively set it to all models.

• deepmd/pt/train/training.py: Modified the gradient clipping function to include the error_if_nonfinite parameter, and removed the manual check for non-finite gradients and the associated exception raising.

Summary by CodeRabbit

• New Features

  • Improved training loop with enhanced error handling and control flow.
  • Updated gradient clipping logic for better error detection.
  • Refined logging functionality for training and validation results.

• Bug Fixes

  • Prevented redundant training calls by adding conditional checks.

• Documentation

  • Clarified method logic in the Trainer class without changing method signatures.

[coderabbitai]

📝 Walkthrough

<details>
<summary>📝 Walkthrough</summary>

## Walkthrough
The pull request introduces modifications to the `Trainer` class in `deepmd/pt/train/training.py`, focusing on enhancing the training loop's control flow and error handling. Key changes include the introduction of an error handling mechanism in the gradient clipping logic, improved logging for training and validation metrics, and adjustments to ensure that the training state is managed effectively. Several methods within the class have had their logic updated without changing their signatures.

## Changes

| File Path                     | Change Summary                                                                                      |
|-------------------------------|----------------------------------------------------------------------------------------------------|
| deepmd/pt/train/training.py   | - Modified training loop to include a check for `self.wrapper.train()` after evaluation.          |
|                               | - Updated gradient clipping logic with `error_if_nonfinite=True`.                                 |
|                               | - Enhanced logging functionality for clearer training and validation results.                      |
|                               | - Multiple method logic updates in `Trainer` class without changing method signatures.            |

## Possibly related PRs
- #4212: This PR modifies the logging and management of training steps in `deepmd/pt/train/training.py`, which is directly related to the changes made in the `Trainer` class regarding training state management and logging enhancements.

## Suggested reviewers
- wanghan-iapcm
- iProzd

</details>

---

📜 Recent review details

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Review profile: CHILL

📥 Commits

Reviewing files that changed from the base of the PR and between 078e848 and 97c3fcf.

📒 Files selected for processing (1)

• deepmd/pt/train/training.py (4 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• deepmd/pt/train/training.py

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.64%. Comparing base (e7ad8dc) to head (97c3fcf).
Report is 5 commits behind head on devel.

Additional details and impacted files

@@           Coverage Diff           @@
##            devel    #4426   +/-   ##
=======================================
  Coverage   84.64%   84.64%           
=======================================
  Files         614      614           
  Lines       57135    57136    +1     
  Branches     3486     3488    +2     
=======================================
+ Hits        48364    48365    +1     
+ Misses       7645     7644    -1     
- Partials     1126     1127    +1     

☔ View full report in Codecov by Sentry.
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[caic99]

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