[Custom template] Overview page

### Issue description
Custom templates - Overview page updates. The following labels and strings have been approved by content.

- ToC section title: Template
- CTA button label: Manage template
- CTA icon: Gear
- Publish button label: Publish

Empty state section:
- Title: Manage your template
- Body: Locate, add, and edit workflows, review connections, set parameters, and more. Save your work anytime and pick up where you left off without having to publish. To publish your template, all fields must be completed.
- Learn more link: Title same as learn more doc
- CTA button: Manage template