[dashboard] Add commit date & fix date related issues (#89517)
Add commit date to build summary of dashboard. Make the date of the run reflective of when the run started, not when the run ended. Use PST (UTC -8) to determine day, rather than GMT (UTC +0).
Test comment: https://github.com/pytorch/torchdynamo/issues/1831#issuecomment-1324176119
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89517
Approved by: https://github.com/anijain2305
