feat(framework:reliability): Allow clients to exit gracefully

[charlesbvll]

Issue

Description

• Currently we have to press Ctrl+C 2 times to exit the flower-client-app in some cases
• The flower-client-app doesn't exit gracefully
• When exiting, the nodes aren't removed from the Superlink, creating "phantom" clients

Related issues/PRs

N/A

Proposal

Explanation

Catch the interrupt exception and send delete_node message when possible.

Checklist

• [x] Implement proposed change
• [x] Update the changelog entry below
• [x] Make CI checks pass
• [x] Ping maintainers on Slack (channel #contributions)

Changelog entry

Any other comments?

N/A