Create pipeline schedule form in Vue

What does this MR do and why?

This addresses #371987 (closed)

The mutations to create and update pipeline schedules will be handled in #385101 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable the pipeline_schedules_vue feature flag in the console

   echo "Feature.enable(:pipeline_schedules_vue)" | bundle exec rails c

2. Visit any project and go to the pipeline schedules page
3. Since the create_button is being worked on as part of this issue, you can add the /new suffix to the URL in your web browser so you can see the new form

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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