Part 1 - Improve Snippets form UX with description field

• Part 1 - Improve Snippets form UX with description field (!24762 (merged))
• Part 2 - Update snippets empty state text and buttons (!24764 (merged))

What does this MR do?

This MR improves some UX of the snippets form

• Reordering the fields in the snippets form
• Specifying that description is optional
• Add "collapsible" behavior to description input

Screenshots

Snippets form	Snippets form with description expanded	Demo
		20200209_snippets_ux_demo

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

References

• #32714 (closed)