Add support select Bitbucket Server (or Cloud) on the multi-branch Pipeline page

Created by: LinuxSuRen

What would you like to be added: Add support select Bitbucket Server (or Cloud) on the multi-branch Pipeline page.

The API request

GET v1alpha2/scms/bitbucket-server/servers

A sample of response JSON:

[
 {
  "id": "c3dfc9f264ee8dfcf787994435364652e79be7208855152f37bd112f4ea5c531",
  "name": "private",
  "apiUrl": "http://103.61.37.132:7991"
 }
]

I'd like to suggest that display the API URL in the select list. In the meantime, we need to let users type a new address as well.

/area devops /priority medium

Why is this needed: Always letting users input type the same Bitbucket server address is not necessary.