linux: scrolling improvements (#9103)

This PR adjusts scrolling to be a lot faster on Linux and also makes
terminal scrolling work.

For Wayland, it makes scrolling faster by handling the `AxisValue120`
event (which also allows high-resolution scrolling on supported mice)
On X11, changed the 1 line per scroll to 3.

### Different solutions

I tried replicating Chromium's scrolling behaviour, but it was
inconsistent in X11/Wayland and found it too fast on Wayland. Plus, it
also didn't match VSCode, since it seems that they do something
different.

Release Notes:

- Made scrolling faster on Linux
- Made terminal scroll on Linux

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

@@ -30,6 +30,8 @@ use crate::{
 
 use super::x11::X11Client;
 
+pub(super) const SCROLL_LINES: f64 = 3.0;
+
 #[derive(Default)]
 pub(crate) struct Callbacks {
     open_urls: Option<Box<dyn FnMut(Vec<String>)>>,