Support to select Gitlab servers and related projects in the Gitlab multi-branch Pipeline

Created by: LinuxSuRen

What would you like to be added: Offer a select for Gitlab multi-branch Pipeline setting page.

Getting server list

Request: GET /v1alpha2/devops/${devops}/jenkins/gitlab/serverList Response : {"status":"ok","data":[{"name":"default","url":"https://gitlab.com"}]}

It means users can choose the items of Git Server. See also the following screenshot:

Geting project list

Request: GET /v1alpha2/devops/${devops}/jenkins/gitlab/projectList?server=${serverName}&owner=${owner} Response: {"status":"ok","data":["LinuxSuRen1/jenkins-cli","LinuxSuRen1/test"]}

It means users can choose the items of Repository Name. See also the following screenshot:

Why is this needed: Make it be easier for users to set up a Gitlab multi-branch Pipeline.