[Enhancement][Nightly playground]Add Notifications stack along with child components

[gaiksaya]

Is your feature request related to a problem? Please describe.
This is a placeholder issue for notifications stack. See #130 for more details

Describe the solution you'd like
TBD

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[gaiksaya]

We decided to go with inbuilt notification system that OpenSearch provides.

Steps:

1. Register a snapshot repo (will be using s3 as it is convenient with cdk)
2. Set up channel and monitors to monitor cluster state. This includes red cluster, high jvm, node drop.
3. Take a snapshot
4. Use the snapshot to restore ".opendistro-alerting-config,.opensearch-notifications-config" in each cluster.

[gaiksaya]

The system indices have problem being restored. Will be using APIs to configure notifications and alerts.