fix(kms): set proper node regions in multi-dc setups

The AWS-KMS code in DB node python class uses shared dictionary
from the DB cluster class for updating the KMS endpoint region.

It was not a problem when DB nodes setup was serial.
In this case shared object was changed by each node but had proper
value in needed time frame.

After implementation of the parallel DB nodes setup [1] we started
getting problems that only one state of that shared object was
being applied for all nodes.

In single-dc setups everything was correct just because there was no
diff among DB node's region names.
But in multi-dc setups values from DB nodes started being applied
to each other.

So, fix it by just deep-copying that shared dictionary to avoid
updates of a shared object.

[1] #7383

Closes: #9025
(cherry picked from commit ce56367)

sdcm/cluster.py

@@ -15,6 +15,7 @@
 from __future__ import annotations
 
 import contextlib
+import copy
 import queue
 import logging
 import os
@@ -514,7 +515,7 @@ def proposed_scylla_yaml(self) -> ScyllaYaml:
             scylla_yml.replace_address_first_boot = self.replacement_node_ip
         if self.replacement_host_id:
             scylla_yml.replace_node_first_boot = self.replacement_host_id
-        if append_scylla_yaml := self.parent_cluster.params.get('append_scylla_yaml') or {}:
+        if append_scylla_yaml := copy.deepcopy(self.parent_cluster.params.get('append_scylla_yaml')) or {}:
             if any(key in append_scylla_yaml for key in (
                     "system_key_directory", "system_info_encryption", "kmip_hosts")):
                 install_encryption_at_rest_files(self.remoter)