[Alerting] action validators should be passed allow-list config utils

[pmuellr]

While reviewing PR #63450, and thinking about moving the code that PR adds to the actions plugin to a case-specific plugin, it seems like we need to expose our whitelisting validating checks, which are currently private to the actions plugin.

Here's an example usage:

kibana/x-pack/plugins/actions/server/builtin_action_types/pagerduty.ts

Lines 121 to 135 in e09e6a2

	function valdiateActionTypeConfig(
	configurationUtilities: ActionsConfigurationUtilities,
	configObject: ActionTypeConfigType
	) {
	try {
	configurationUtilities.ensureWhitelistedUri(getPagerDutyApiUrl(configObject));
	} catch (whitelistError) {
	return i18n.translate('xpack.actions.builtin.pagerduty.pagerdutyConfigurationError', {
	defaultMessage: 'error configuring pagerduty action: {message}',
	values: {
	message: whitelistError.message,
	},
	});
	}
	}

See the code above that to see how configObject is curried onto the validator params.

I think what we should probably do is add an optional validatorServices parameter object to all the validators - config, secrets, params (params not technically needed at this point, but might as well be consistent, and maybe needed in the future). Validators that need to whitelist will then just get the APIs needed to do the check in that object, without having to curry. Those that don't, won't need to change.

[elasticmachine]

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

[pmuellr]

At this point, the scope has moved beyond the allow list. It should also take into account the proxy and http/https agent in general, and probably the axios utilities.