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 91.32420% with 19 lines in your changes missing coverage. Please review.

Project coverage is 82.21%. Comparing base (09a46f9) to head (cf3fde9).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...rover/python/master/diagnosis/diagnosis_manager.py	89.18%	4 Missing ⚠️
dlrover/python/elastic_agent/master_client.py	25.00%	3 Missing ⚠️
...rover/python/master/diagnosis/precheck_operator.py	91.17%	3 Missing ⚠️
dlrover/python/master/servicer.py	60.00%	2 Missing ⚠️
dlrover/trainer/torch/elastic_run.py	83.33%	2 Missing ⚠️
dlrover/python/master/args.py	88.88%	1 Missing ⚠️
dlrover/python/master/diagnosis/diagnosis.py	50.00%	1 Missing ⚠️
dlrover/python/master/main.py	0.00%	1 Missing ⚠️
dlrover/python/master/node/job_context.py	90.00%	1 Missing ⚠️
dlrover/python/tests/test_pre_check_operator.py	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1453      +/-   ##
==========================================
+ Coverage   82.14%   82.21%   +0.06%     
==========================================
  Files         253      255       +2     
  Lines       25288    25498     +210     
==========================================
+ Hits        20774    20964     +190     
- Misses       4514     4534      +20     

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[samplise]

lgtm