PAC: Correct variable support for Bitbucket data center

Many of our Red Hat customers rely on Bitbucket Data Center for their source code management needs. Pipelines as Code (PAC) as tightly integrating with SCM providers to ensure a seamless GitOps experience, depends a lot on SCM APIS. While our upstream documentation mentions support for Bitbucket Cloud and Data Center in PAC (referenced here: Bitbucket Server Installation Guide), thorough end-to-end testing has been lacking. This gap has led to reported issues, especially concerning PAC variables, causing frustration for users during implementation. Our focus has primarily been on GitHub (GH) testing, creating a disparity that needs to be addressed.