Implement computer-to-device clipboard copy

It was already possible to _paste_ (with Ctrl+v) the content of the
computer clipboard on the device. Technically, it injects a sequence of
events to generate the text.

Add a new feature (Ctrl+Shift+v) to copy to the device clipboard
instead, without injecting the content. Contrary to events injection,
this preserves the UTF-8 content exactly, so the text is not broken by
special characters.

<https://github.com/Genymobile/scrcpy/issues/413>

README.md

@@ -289,6 +289,7 @@ you are interested, see [issue 14].
  | collapse notification panel            | `Ctrl`+`Shift`+`n`            |
  | copy device clipboard to computer      | `Ctrl`+`c`                    |
  | paste computer clipboard to device     | `Ctrl`+`v`                    |
+ | copy computer clipboard to device      | `Ctrl`+`Shift+`v`             |
  | enable/disable FPS counter (on stdout) | `Ctrl`+`i`                    |
 
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