New precheck procedure to enhance stability.

[BalaBalaYi]

What changes were proposed in this pull request?

1. Pre-check operator api definition.
2. Design doc.
3. Base implement of pre-check procedure including master and worker.

Why are the changes needed?

For details, please see the design document in the current PR.

Does this PR introduce any user-facing change?

User can enable or disable the pre-check function through job args. For details, please see the development document in the current PR.

How was this patch tested?

UT and simple training job.

[codecov]

Codecov Report

Attention: Patch coverage is 92.07921% with 16 lines in your changes missing coverage. Please review.

Project coverage is 81.59%. Comparing base (03c965f) to head (3ace0da).

Files with missing lines	Patch %	Lines
...rover/python/master/diagnosis/diagnosis_manager.py	89.18%	4 Missing ⚠️
...rover/python/master/diagnosis/precheck_operator.py	91.17%	3 Missing ⚠️
dlrover/python/elastic_agent/master_client.py	33.33%	2 Missing ⚠️
dlrover/python/master/servicer.py	60.00%	2 Missing ⚠️
dlrover/python/master/args.py	88.88%	1 Missing ⚠️
dlrover/python/master/diagnosis/diagnosis.py	50.00%	1 Missing ⚠️
dlrover/python/master/node/job_context.py	88.88%	1 Missing ⚠️
dlrover/python/tests/test_pre_check_operator.py	94.11%	1 Missing ⚠️
dlrover/trainer/torch/elastic_run.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1453      +/-   ##
==========================================
+ Coverage   81.53%   81.59%   +0.06%     
==========================================
  Files         240      242       +2     
  Lines       23592    23788     +196     
==========================================
+ Hits        19235    19411     +176     
- Misses       4357     4377      +20     

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