PGO: Improve the existing PR process

[1pkg]

Description

As a followup of #13859 the existing PGO PR process could be further improved to reduce the notification noise and manual interactions required to merge the PGO PRs.

The following changes need be implemented :

• Automate diff validation process of CPU profiles, bake the difference between the profiles into PR description. So no manual validation is required.
• Reuse the same branch name when opening a new PGO PR thus preventing stale changes.
• Reduce Github action running cadence to a single run per 30 days. As the existing schedule proven to be excessive.