[connectors] Allow connector UX to display warnings about connectors

[pmuellr]

in PR #105440, a new capability in the connectors UX is added - the ability to display a warning icon beside a connector. This is used in the PR to note connectors which are "deprecated" and need to be updated.

The way this is done in the PR is to check a specific field for a specific set of connector types:

kibana/x-pack/plugins/triggers_actions_ui/public/application/sections/actions_connectors_list/components/actions_connectors_list.tsx

Lines 176 to 183 in 409e31d

	const itemConfig = (
	item as UserConfiguredActionConnector<Record<string, unknown>, Record<string, unknown>>
	).config;
	const showLegacyTooltip =
	itemConfig?.isLegacy &&
	// TODO: Remove when applications are certified
	((ENABLE_NEW_SN_ITSM_CONNECTOR && item.actionTypeId === '.servicenow') ||
	(ENABLE_NEW_SN_SIR_CONNECTOR && item.actionTypeId === '.servicenow-sir'));

That code will get complicated if we need to add more of these.

Rather than continue in that style, it seems like a connector should be able to return some kind of "warning" indicator, that would have at least the content needed for the tooltip - title and content. Perhaps we'd also want to allow a customized icon, and a URL (in case the warning message is actionable, and the URL would help the user perform that action).

If we have a generic way of allowing a connector to return this kind of information, then we can move that logic into the connectors, and out of the generic UX code.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[gmmorris]

We should probably do this as part of the oAuth support work as we'll need a way of warning users when their tokens expire.

Moving to backlog until we have clearer timelines for oAuth.