[Doc]: Can we have document for variables AZURE_PS_HTTP_MAX_RETRIES and AZURE_PS_HTTP_MAX_RETRIES_FOR_429

### Description

Hi,
Can you document the variables mentioned here: https://github.com/Azure/azure-powershell/issues/14504
Also can you be more specific how these variables affect the usage of Az?
Can these variables be used to avoid errors like: "The operation was canceled." Such error appears from time to time and it is unclear what is the exact problem.