[Part 3] Migrate connection UI metadata to YAML for more providers

[amoghrajesh]

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Was generative AI tooling used to co-author this PR?

• Yes - cursor IDE

Handled the providers mainly used for notifiers, listeners, or alerting.

1. Slack
2. Discord
3. Pagerduty
4. Opsgenie
5. SMTP
6. Telegram
7. Apprise

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[jason810496]

Thanks Amogh!