Add a copy/duplicate button to Lexical blocks

[LordSimal]

We already have copy paste functionality for lexcial blocks via #11513

But the UX of doing it is kind of tidious / not really self explenatory as one has to

• open the block one wants to copy
• click inside the block but NOT inside a field to make it "active" which is indicated by a blue outline on the block
• press Ctrl + C (or CMD + C)
• go to the place where you can to paste the block and press Ctrl + V (or CMD + V)

It would be nice to have a simple "Copy" Button next to the delete button right here

Then its easier to just move the already existing duplicated block instead of having to find the right focus on the block one needs to copy.