Add an opt-in Sync clipboard setting

[Wouze]

Summary

• Add a Settings checkbox, Sync clipboard, saved as syncclipboard and off by default.
• When it is on, the client subscribes at stream start and keeps UTF-8 clipboard text in sync with a Sunshine host that supports it.
• Ctrl+Alt+Shift+V is unchanged for older hosts.
• The submodule moonlight-common-c points at Add an opt-in text clipboard packet moonlight-common-c#155 (cfd661028220a2c1bb8536cb49b2573f1a317f90).

Test plan

• Linux AppImage, Sync clipboard on, copies text both ways with the matching Sunshine host
• Checkbox off does not send or apply clipboard text
• Mac and Windows use the same SDL clipboard path and have not been run

[Wouze]

Hi. I merged current master into this branch. The moonlight-common-c submodule includes that master plus the clipboard protocol from moonlight-stream/moonlight-common-c#155. Could you review this once that protocol change is in?

[Wouze]

Hi @cgutman

This depends on moonlight-common-c#155, which ReenigneArcher already approved. Could you review the Sync clipboard setting when you have time?

Thanks