Issue Summary

When create plan branch dialog fetches 1 mln VCS branch names. Every time user types branch name text dialog fetches same data again and again. In case repo has more than 1 mln branches, some of them will be unavailable to choose as they're not returned to user

This is reproducible on Data Center: yes

Steps to Reproduce

1. Create repo with 100k branches
2. Create Bamboo plan with created repo
3. Click Create plan branch button at plan summary
4. Start typing branch name at dialog and see browser fetches 1 mln records every time user types 

Expected Results

Response is filtered by user text, 100 elements are fetched from backend

Actual Results

1 mln records are fetched from backend. If desired branch is outside of this range it's not possible to choose it from list.

Workaround

Use manual plan branch create option.