Quickly copy code blocks in the Content Editor

What does this MR do and why?

Adds a copy button to the recently introduced code block bubble menu to allow easily copying code in a code block.

Related to #330627 (closed)

Screenshots or screen recordings

Screen_Recording_2022-04-20_at_1.18.43_AM

How to set up and validate locally

1. Open any wiki page, and edit
2. Insert a new code block
3. Type in some code
4. Click the "copy to clipboard" icon to copy the code
5. Try pasting the code in the same code block
6. It works!

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.