This PR enables server side decorations on Wayland if possible. This is
stopgap solution, so that the window can be moved, resized and dragged
on Wayland sessions at all.

Since Wayland compositors can decide to force either mode (as in,
forcing server or client side decorations), this requires additional
handling in zed. Since zed doesn't provide any of that handling as of
now, as a temporary solution server side decorations are always
requested.
Release Notes:
- N/A
---
Right now the Wayland backend is using `xkb::State::key_get_utf8` as the
`key`, when it should be used as the `ime_key`. It also manages
pressing/releasing modifiers manually when this should be managed by the
display server.
This allows modifier combinations to work in more cases, making it an
alternative to https://github.com/zed-industries/zed/pull/7975, which
interprets what is now only used as the `ime_key` value as a `key`
value.
Adds initial keyboard and mouse input for Wayland (thanks to @gabydd and
@kvark for reference).
Release Notes:
- N/A
---------
Co-authored-by: Mikayla Maki <mikayla@zed.dev>
This PR adds Wayland support to gpui using
[wayland-rs](https://github.com/Smithay/wayland-rs). It is based on
[#7598](https://github.com/zed-industries/zed/pull/7598).
It detects Wayland support at runtime by checking the existence of the
`WAYLAND_DISPLAY` environment variable. If it does not exist or is
empty, the X11 backend will be used. To use the X11 backend in a Wayland
session (for development purposes), you just need to unset
WAYLAND_DISPLAY (`WAYLAND_DISPLAY= cargo run ...`).
At the moment it only creates the window and renders the initial content
provided by `BladeRenderer`, so it can run "Hello world" example.

Todo:
- [x] Add basic Wayland support.
- [x] Add window resizing.
- [x] Add window closing.
- [x] Add window updating.
- [ ] Implement input handling, fractional scaling, and support other
Wayland protocols.
- [ ] Implement all unimplemented todo!(linux).
- [ ] Add window decorations or use custom decorations (like on MacOS).
- [ ] Address other missing functionality.
Release Notes:
- N/A
---------
Co-authored-by: gabydd <gabydinnerdavid@gmail.com>
Co-authored-by: Mikayla Maki <mikayla@zed.dev>