Enhancement: Show dropdown instead of input field for git branch regex

[pawan-mehta-dt]

🔖 Feature description

Show dropdown instead of input field for git branch regex

🎤 Pitch / Usecases

We want to use Branch Regex for Git Provider but we don't want to enter the branch manually as human intervention with incorrect branch might break the environment. Fetch and display the branches matching with regex in a dropdown to select the branch to start the build.

🔄️ Alternative

We can use input field provided for now

👀 Have you spent some time to check if this issue has been raised before?

• [X] I checked and didn't find similar issue

🏢 Have you read the Code of Conduct?

• [X] I have read the Code of Conduct