refactor: Reuse the git repository selector on the Pipeline and CD page

Created by: bunnymiao

What type of PR is this?

/kind feature

What this PR does / why we need it:

Reuse the git repository selector on the Pipeline and CD page

Which issue(s) this PR fixes:

Fixes #606

Special notes for reviewers:

Does this PR introduced a user-facing change?

NONE

Additional documentation, usage docs, etc.: