Refactor CSS and remove unnecessary overriding styling

Problem/Motivation

I see there is a lot of unecessary CSS that may (usually does) conflict with the site theme, so I wonder if we could make all of that optional by providing an "unstyled" formatter or with a global config setting.
Any theme (example in core) has a way of showing buttons, input texts, etc.. and defines his font-size, colors, etc.. so why override them?

Proposed resolution

I would remove all of these CSS:
on the input.clipboardjs:

and similarly on the .clipboardjs-button. There and in the clipboard text (if shown in an input text or similar) I would set the border-radius to "match" coming from left and right, like: x 0 0 x|0 x x 0, which is not the case right now.

Also notice that the clipboard text is not centered relative to the button:

If this is not easily achievable I would abandon the text centering and put the tip to the left x/2 position where x = the button's width.

Remaining tasks

Collect other proposals and feedbacks, possibly with other themes (than Claro) as well.