Add new action to OpsGenieWebhook for apprise==1.9.0 compatibility

[kevingrismore]

apprise's new default MAP action for OpsGenie is a no-op (no notification is sent). To create an OpsGenie alert we need to include the new action type. As is, this is backwards compatible with older apprise versions, but if we bumped the minimum requirement for apprise to 1.9.0 we could either import and use OpsgenieAlertAction.NEW or maybe even support action as a block field instead of just sending a string.

Checklist

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[codspeed-hq]

CodSpeed Performance Report

Merging #16030 will not alter performance

_{Comparing opsgenie-action (b16a425) with main (a98b938)}

Summary

✅ 3 untouched benchmarks

[zzstoatzz]

lgtm!