wayland: Refactor clipboard implementation (#12405)

Fixes https://github.com/zed-industries/zed/issues/12054

Replaces the `copypasta`/`smithay-clipboard` implementation with a new,
custom one

TODO list:

- [x] Cleanup code
- [x] Remove `smithay-clipboard`
- [x] Add more mime types to the supported list

Release Notes:

- Fixed drag and drop on Gnome
- Fixed clipboard paste on Hyprland

crates/gpui/src/platform/linux/platform.rs

@@ -22,7 +22,6 @@ use ashpd::desktop::file_chooser::{OpenFileRequest, SaveFileRequest};
 use async_task::Runnable;
 use calloop::channel::Channel;
 use calloop::{EventLoop, LoopHandle, LoopSignal};
-use copypasta::ClipboardProvider;
 use filedescriptor::FileDescriptor;
 use flume::{Receiver, Sender};
 use futures::channel::oneshot;