fix(cli): Make --watcher CLEAR_SCREEN clear scrollback buffer as well as visible screen (denoland#25997)

The --watch option should clear the screen scrollback buffer as well as
the screen itself.

On Ubuntu (22.04 Jammy) the 'clear' command generates
"\x1B[H\x1B[2J\x1B[3J"; that is:
- \E[H  - cursor home
- \E[2J - clear entire screen
- \E[3J - clear entire screen & scrollback buffer.

By contrast, Deno defined CLEAR_SCREEN as "\x1B[2J\x1B[1;1H", which
fails to clear the scrollback buffer.

The "\E[H\E[2J\E[3J" sequence works on MacOS (Sonoma) (using printf);
I'm not able to test on Windows.

Closes denoland#26514

Author: chrisveness

cli/util/file_watcher.rs

@@ -30,7 +30,7 @@ use tokio::sync::mpsc;
 use tokio::sync::mpsc::UnboundedReceiver;
 use tokio::time::sleep;
 
-const CLEAR_SCREEN: &str = "\x1B[2J\x1B[1;1H";
+const CLEAR_SCREEN: &str = "\x1B[H\x1B[2J\x1B[3J";
 const DEBOUNCE_INTERVAL: Duration = Duration::from_millis(200);
 
 struct DebouncedReceiver {