Fix double prompt issue in network_cli (#35439)

Fixes #33993

In current implementation while trying to fetch the
current cli prompt terminal plugin executes `\r` on remote host.

This causes if command execution results in a prompt for
example executing `enable` command results in `Password:` prompt
there by executing `\r` on password prompt which is not intended.

To fix it while fetching current prompt from terminal plugin use `get_prompt()`
api in network_cli that returns the latest matched prompt instead of
unnecessary executing `\r` on remote host.

lib/ansible/plugins/terminal/__init__.py

@@ -69,11 +69,7 @@ class TerminalBase(with_metaclass(ABCMeta, object)):
 
         :returns: A byte string of the prompt
         """
-        # do not send '\n' here, exec_cli_command sends '\r' already,
-        # doing so causes double prompts.
-        self._exec_cli_command(b'')
-
-        return self._connection._matched_prompt
+        return self._connection.get_prompt()
 
     def on_open_shell(self):
         """Called after the SSH session is established