New exitcode for SCP not found

Re: https://github.com/saltstack/salt/issues/25478 and https://github.com/saltstack/salt/issues/25026

salt/client/ssh/__init__.py

@@ -1048,6 +1048,11 @@ ARGS = {9}\n'''.format(self.minion_config,
                 'checksum mismatched',
                 'The salt thin transfer was corrupted'
             ),
+            (
+                (salt.defaults.exitcodes.EX_SCP_NOT_FOUND,),
+                'scp not found',
+                'No scp binary. openssh-clients package required'
+            ),
             (
                 (salt.defaults.exitcodes.EX_CANTCREAT,),
                 'salt path .* exists but is not a directory',

salt/client/ssh/ssh_py_shim.py

@@ -24,6 +24,7 @@ EXT_ARCHIVE = 'salt-ext_mods.tgz'
 EX_THIN_DEPLOY = 11
 EX_THIN_CHECKSUM = 12
 EX_MOD_DEPLOY = 13
+EX_SCP_NOT_FOUND = 14
 
 
 class OBJ(object):

salt/defaults/exitcodes.py

@@ -14,6 +14,7 @@ EX_THIN_PYTHON_OLD = 10
 EX_THIN_DEPLOY = 11
 EX_THIN_CHECKSUM = 12
 EX_MOD_DEPLOY = 13
+EX_SCP_NOT_FOUND = 14
 
 # The os.EX_* exit codes are Unix only so in the interest of cross-platform
 # compatiblility define them explicitly here.