terminal: Fix escaping arguments when using CMD as the shell (#39701)

A couple of caveats:
- We should not auto-escape arguments with Alacritty's `escape_args`
option if using CMD otherwise, the generated command will have way too
many escaped characters for CMD to parse correctly.
- When composing a full command for CMD, we need to put it in double
quotes manually: `cmd /C "activate.bat& pwsh.exe -C do_something"` so
that CMD executes the entire string as a sequence of commands.
- CMD requires `&` as a chaining operator for commands (`;` for other
shells).

Release Notes:

- N/A

crates/task/src/shell_builder.rs

@@ -49,7 +49,7 @@ impl ShellBuilder {
                     format!("{} -C '{}'", self.program, command_to_use_in_label)
                 }
                 ShellKind::Cmd => {
-                    format!("{} /C '{}'", self.program, command_to_use_in_label)
+                    format!("{} /C \"{}\"", self.program, command_to_use_in_label)
                 }
                 ShellKind::Posix
                 | ShellKind::Nushell

crates/task/src/task.rs

@@ -345,6 +345,7 @@ impl Shell {
             Shell::System => get_system_shell(),
         }
     }
+
     pub fn program_and_args(&self) -> (String, &[String]) {
         match self {
             Shell::Program(program) => (program.clone(), &[]),
@@ -352,6 +353,14 @@ impl Shell {
             Shell::System => (get_system_shell(), &[]),
         }
     }
+
+    pub fn shell_kind(&self) -> ShellKind {
+        match self {
+            Shell::Program(program) => ShellKind::new(program),
+            Shell::WithArguments { program, .. } => ShellKind::new(program),
+            Shell::System => ShellKind::system(),
+        }
+    }
 }
 
 type VsCodeEnvVariable = String;