Additional improvements to the Trigger Pipeline experience in the CircleCI web app

Updates:

• Added a ‘Remove all’ button to allow users to easily remove parameters for specific projects
• We display in-modal error states when users input duplicate parameter names, have a missing config file in their selected branch, etc.
• When users manually add a parameter, the new row will now appear at the top of the list instead of the bottom, making it easier to spot and fill in