auto_update: Offload update installation to background thread

[lingyaochu]

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Closes #55279

When auto-updating, Zed first downloads the update and then performs the installation. On each platform, this installation phase runs external commands that spawn new processes. These operations can block the thread they run on—especially under heavy system load or when security/antivirus software is active. (An analysis of the blockages on Windows is documented in #55279 (comment)).

This PR moves the installation process to a background thread. This ensures that even if process spawning block, the main UI thread remains responsive.

Release Notes:

• Fixed a UI freeze that could occur when installing auto-updates.

[zed-industries-bot]

	Messages
📖	This PR includes links to the following GitHub Issues: #55279 If this PR aims to close an issue, please include a Closes #ISSUE line at the top of the PR body.

Generated by 🚫 dangerJS against e842442

[lingyaochu]

zed/crates/auto_update/src/auto_update.rs

Lines 1161 to 1185 in f99fe5d

	#[cfg(test)]
	mod tests {
	use client::Client;
	use clock::FakeSystemClock;
	use futures::channel::oneshot;
	use gpui::TestAppContext;
	use http_client::{FakeHttpClient, Response};
	use settings::default_settings;
	use std::{
	rc::Rc,
	sync::{
	Arc,
	atomic::{self, AtomicBool},
	},
	};
	use tempfile::tempdir;
	#[ctor::ctor(unsafe)]
	fn init_logger() {
	zlog::init_test();
	}
	use super::*;
	pub(super) struct InstallOverride(pub Rc<dyn Fn(&Path, &AsyncApp) -> Result<Option<PathBuf>>>);

InstallOverride is defined in tests with #[cfg(test)], which is conditionally compiled, so cfg!(test) maybe not suitable here.

Revert of the update changes? Or any other suggestions?

[Veykril]

lets gate the let install_result = ... line then with #[cfg(test)] and #[cfg(not(test))] respectvely instead of doing the branching

[lingyaochu]

This line is added to make the script/clippy happy