Fixed alignment of snippet clone copy btns

What does this MR do?

Exactly what the title says: the MR fixes alignment of the icons ion the Snippet → Clone → Copy buttons.

On the way, this MR also refactors the copy buttons to use native icon prop on gl-button instead of explicitly putting gl-icons as the content of the buttons.

Screenshots

Before	After

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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

References #216035 (closed)