fix: sliding expiration cache concurrent access exceptions

[faviansamatha]

Description

Sliding expiration cache is not thread safe. When manually testing with 30 threads executing a query and triggering failover with the failover_v2, the following error could be displayed:

aws_advanced_python_wrapper.FailoverSuccessError: [Failover] The active SQL connection has changed due to a connection failure. Please re-configure session state if required.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/app/tests/integration/container/dummy/test_failover_race_condition.py", line 254, in long_running_query
    with AwsWrapperConnection.connect(
  File "/app/aws_advanced_python_wrapper/wrapper.py", line 232, in __exit__
    self.release_resources()
  File "/app/aws_advanced_python_wrapper/wrapper.py", line 220, in release_resources
    self._plugin_service.release_resources()
  File "/app/aws_advanced_python_wrapper/plugin_service.py", line 740, in release_resources
    host_list_provider.release_resources()
  File "/app/aws_advanced_python_wrapper/host_list_provider.py", line 810, in release_resources
    MonitoringRdsHostListProvider._monitors.clear()
  File "/app/aws_advanced_python_wrapper/utils/sliding_expiration_cache.py", line 99, in clear
    for _, cache_item in self._cdict.items():
RuntimeError: dictionary changed size during iteration

items(), keys(), and values() are not thread-safe when a piece of code is iterating over them. They must first be converted to a list.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.