fix(windows): fix windows terminal ANSI escape sequences (#2258)

* fix(windows): don't inherit stdin when executing commands

On Windows, inheriting stdin from starship might lead to leaking the
console reference to the command we're executing. `id.exe` supplied with
Git has been observed to disable the ENABLE_VIRTUAL_TERMINAL_PROCESSING
console flag if it inherits stdin -- leading to Windows Terminal not
processing ANSI escape sequences.

This change fixes #2254 by explicitly disabling stdin inheritance.

The fix was suggested by David Knaack.

* fix(username): don't call `id -u` on Windows

This was done to check if user is root by comparing the UID to 0. Windows
does not have a concept of UID 0 anyway, so it's pointless to call `id.exe`
(which is installed with MSYS2 or Git, for example).

src/utils.rs

@@ -277,6 +277,7 @@ fn internal_exec_cmd(cmd: &str, args: &[&str]) -> Option<CommandOutput> {
         .args(args)
         .stderr(Stdio::piped())
         .stdout(Stdio::piped())
+        .stdin(Stdio::null())
         .spawn()
     {
         Ok(process) => process,