PR-Content-Check GH Workflow Optimization: Check the accumulated content change instead of only check the last commit.

[linlin-s]

PR-Content-Check is the GH workflow used for checking the content of the incoming PR and then decide to execute the Performance-Regression-Detection workflow or skip the workflow. For now, when there is a new commit added to the current PR, the PR-Content-Check will be trigger and it will check the content change for the new commit. If there is no source code change in the new commit but there was source code change in the previous commit within the same PR, the final workflow run will show that the regression detection has been skipped which is from the most recent commit, and the workflow run of the previous commit will be hidden by the new one. Here is an example from this PR: If we check the details of this PR, we can still see the workflow run results for each commit:

Even though we can still retrieve the workflow run for specific commit, it is confusing for users to read the final results. To resolve this problem, we should optimizing the PR-Content-Check workflow to cache the content check results from the previous change then use the accumulated results to decide whether to trigger the regression detection workflow or not.