Make MaxPullRequestPollCount configurable via YAML

[Kamalesh-Seervi]

Description: In large organizations with automated PR merges, the current hardcoded limit of 5 retries for the MaxPullRequestPollCount parameter in bulldozer/merge.go can become a bottleneck. When bulldozer stops after 5 retries, it may not be sufficient for many workflows, leading to potential merge delays.

Proposal: Please make the MaxPullRequestPollCount parameter configurable via the bulldozer YAML configuration file. This change would allow organizations to customize the retry count based on their specific requirements and workflows.

Benefits:

Flexibility for organizations to set their own retry count.
Reduces likelihood of bulldozer stopping prematurely, improving efficiency.

And I would like work on this issue

[bluekeyes]

While I'm not opposed to making this configurable, could you share more details about the failures you're seeing in large organizations that would be fixed by more retries? There may be other options to fix the issues that are worth considering.