Wayland: double click (#9608)

This PR builds off of an earlier version of
https://github.com/zed-industries/zed/pull/9595, rearranges some of the
logic, and removes an unused platform API.

Release Notes:

- N/A

---------

Co-authored-by: apricotbucket28 <agustin.nicolas.marcos@outlook.com>

crates/gpui/src/platform/test/platform.rs

@@ -12,7 +12,6 @@ use std::{
     path::PathBuf,
     rc::{Rc, Weak},
     sync::Arc,
-    time::Duration,
 };
 
 /// TestPlatform implements the Platform trait for use in tests.
@@ -303,10 +302,6 @@ impl Platform for TestPlatform {
         Task::ready(Ok(()))
     }
 
-    fn double_click_interval(&self) -> std::time::Duration {
-        Duration::from_millis(500)
-    }
-
     fn register_url_scheme(&self, _: &str) -> Task<anyhow::Result<()>> {
         unimplemented!()
     }