Add basic bash and Python tasks (#10548)

Part of https://github.com/zed-industries/zed/issues/5141

* adds "run selection" and "run file" tasks for bash and Python.
* replaces newlines with `\n` symbols in the human-readable task labels
* properly escapes task command arguments when spawning the task in
terminal

Caveats:

* bash tasks will always use user's default shell to spawn the
selections, but they should rather respect the shebang line even if it's
not selected
* Python tasks will always use `python3` to spawn its tasks now, as
there's no proper mechanism in Zed to deal with different Python
executables

Release Notes:

- Added tasks for bash and Python to execute selections and open files
in terminal

crates/terminal/src/terminal.rs

@@ -286,6 +286,7 @@ impl Display for TerminalError {
     }
 }
 
+#[derive(Debug)]
 pub struct SpawnTask {
     pub id: TaskId,
     pub full_label: String,