auth-backend: migrate bitbucketserver provider to separate module

[JeevaRamanathan]

Hey, I just made a Pull Request!

This relates to https://github.com/backstage/backstage/issues/19476

:heavy_check_mark: Checklist

• [x] A changeset describing the change and affected packages. (more info)
• [x] Added or updated documentation
• [ ] Tests for new functionality and regression tests for bug fixes
• [ ] Screenshots attached (for UI changes)
• [x] All your commits have a Signed-off-by line in the message. (more info)

[backstage-goalie[bot]]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@backstage/plugin-auth-backend-module-bitbucketServer-provider	plugins/auth-backend-module-bitbucketServer-provider	minor	v0.1.15-next.1
@backstage/plugin-auth-backend	plugins/auth-backend	minor	v0.22.5-next.1

[github-actions[bot]]

Uffizzi Ephemeral Environment - Virtual Cluster

Your cluster pr-24607 was successfully created. Learn more about Uffizzi virtual clusters To connect to this cluster, follow these steps:

1. Download and install the Uffizzi CLI from https://docs.uffizzi.com/install
2. Login to Uffizzi, then select the backstage account and project:

   uffizzi login

Select an account: 
  ‣ backstage
    jdoe

Select a project or create a new project: 
  ‣ backstage-6783521

3. Update your kubeconfig: uffizzi cluster update-kubeconfig pr-24607 --kubeconfig=[PATH_TO_KUBECONFIG] After updating your kubeconfig, you can manage your cluster with kubectl, kustomize, helm, and other tools that use kubeconfig files: kubectl get namespace --kubeconfig [PATH_TO_KUBECONFIG]

Access the backstage endpoint at https://backstage-default-pr-24607-c5378.uclusters.app.uffizzi.com

[JeevaRamanathan]

Hi @Rugvip @freben, Could you please review the PR and provide suggestions if it's on right track and any changes to be done?