CloudTrail advanced selectors support

[ajkerrigan]

CloudTrail advanced selectors support

[anna-shcherbak]

I do not know if it's a good idea, but what if we reuse the aws.cloudtrail.event-selectors in other places? I haven't found any similar examples in the code, so maybe it's not the best way to do this.
For example in aws.account.check-cloudtrail, the part with the include-management-events check can be rewritten from this:

cloud-custodian/c7n/resources/account.py

Lines 289 to 297 in 07c86ff

	if self.data.get('include-management-events'):
	matched = []
	for t in list(trails):
	selectors = client.get_event_selectors(TrailName=t['TrailARN'])
	if 'EventSelectors' in selectors.keys():
	for s in selectors['EventSelectors']:
	if s['IncludeManagementEvents'] and s['ReadWriteType'] == 'All':
	matched.append(t)
	trails = matched

the following way:

        if self.data.get('include-management-events'):
            matched = []
            for t in list(trails):
                data = {
                    'key': "AdvancedEventSelectors[?FieldSelectors[?Field == 'eventCategory' && "
                           "Equals[?contains(@, 'Management')==`true`]] && "
                           "!(FieldSelectors[?Field=='readOnly'])] || "
                           "EventSelectors[?IncludeManagementEvents==`true` && ReadWriteType=='All']",
                    'value_type': 'size',
                    'op': 'gt',
                    'value': 0
                }
                if len(EventSelectors(data, self.manager).process(trails)) > 0:
                    matched.append(t)
            trails = matched