Document CI retry rules

[huydhn]

With all the recent changes w.r.t retrying to harden PyTorch CI, we need to create a wiki page to document all these mechanisms. The tentative list includes:

• Individual test case retry (flaky bot)
• Retry test file
• Retry on workflow steps (using GHA)
• Retry the job itself (retry bot)

In addition, we also want to gather data points to answer the following questions

• How much resource do we spend on retrying these cases?
• And a rough estimation on how frequently people manually retry stuffs on their PR to get green signals or to debug flaky issue

cc @ZainRizvi @kit1980 @clee2000

[huydhn]

There is also a new log entry to print reproduce command #104537 that we want to include in the wiki

[clee2000]

Main CI wiki page: https://github.com/pytorch/pytorch/wiki/Continuous-Integration
Please feel free to add more info