Fix tasks not being stopped on reruns (#29786)

Follow-up of https://github.com/zed-industries/zed/pull/28993

* Tone down tasks' cancellation logging
* Fix task terminals' leak, disallowing to fully cancel the task by
dropping the terminal off the pane:

https://github.com/zed-industries/zed/blob/f619d5f02af100c34e286af294a42a01dcfb238c/crates/terminal_view/src/terminal_panel.rs#L1464-L1471

Release Notes:

- Fixed tasks not being stopped on reruns

crates/debugger_ui/src/debugger_panel.rs

@@ -6,7 +6,7 @@ use crate::{
     persistence,
 };
 use crate::{new_session_modal::NewSessionModal, session::DebugSession};
-use anyhow::{Result, anyhow};
+use anyhow::{Context as _, Result, anyhow};
 use collections::{HashMap, HashSet};
 use command_palette_hooks::CommandPaletteFilter;
 use dap::DebugRequest;
@@ -500,7 +500,7 @@ impl DebugPanel {
                     workspace.spawn_in_terminal(task.resolved.clone(), window, cx)
                 })?;
 
-                let exit_status = run_build.await?;
+                let exit_status = run_build.await.transpose()?.context("task cancelled")?;
                 if !exit_status.success() {
                     anyhow::bail!("Build failed");
                 }