Clean up Create Branch from Jira form

What does this MR do and why?

Clean up "Create Branch from Jira" form:

• "New branch" => "Create branch"
• Use project avatar in dropdown
• Reorder form elements

Related to #337274 (closed)

Screenshots or screen recordings

before	after

How to set up and validate locally

Navigate to http://gdk.test:3000/-/jira_connect/branches/new

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.