terminal: Log selected shell (#39295)

It is useful to double check in the logs which shell program is used by
Zed's terminal.

Release Notes:

- N/A

crates/terminal/src/terminal.rs

@@ -378,31 +378,40 @@ impl TerminalBuilder {
             title_override: Option<SharedString>,
         }
 
+        impl ShellParams {
+            fn new(
+                program: String,
+                args: Option<Vec<String>>,
+                title_override: Option<SharedString>,
+            ) -> Self {
+                log::info!("Using {program} as shell");
+                Self {
+                    program,
+                    args,
+                    title_override,
+                }
+            }
+        }
+
         let shell_params = match shell.clone() {
             Shell::System => {
                 #[cfg(target_os = "windows")]
                 {
-                    Some(ShellParams {
-                        program: util::get_windows_system_shell(),
-                        ..Default::default()
-                    })
+                    Some(ShellParams::new(
+                        util::get_windows_system_shell(),
+                        None,
+                        None,
+                    ))
                 }
                 #[cfg(not(target_os = "windows"))]
                 None
             }
-            Shell::Program(program) => Some(ShellParams {
-                program,
-                ..Default::default()
-            }),
+            Shell::Program(program) => Some(ShellParams::new(program, None, None)),
             Shell::WithArguments {
                 program,
                 args,
                 title_override,
-            } => Some(ShellParams {
-                program,
-                args: Some(args),
-                title_override,
-            }),
+            } => Some(ShellParams::new(program, Some(args), title_override)),
         };
         let terminal_title_override = shell_params.as_ref().and_then(|e| e.title_override.clone());