Changes from #74641. These changes were already made in master and backported to 7.x. A separate PR was needed for 7.9 because integration tests don't exist in 7.9 and CI would not pass. These are changes that don't try to update integration tests.

Changes

• removes events as a default index pattern type so events-* and the placeholder index will no longer be created
• updates integration test to not expect events-* index pattern to be created
• adds integration test to check that the right placeholder indices were created for logs-* and metrics-* types index patterns (logs-index_pattern_placeholder, metrics-index_pattern_placeholder);

Test

• manually test with a fresh elasticsearch instance after logging into Kibana, ensuring no such index pattern exists (http://localhost:5601/ssg/api/saved_objects/index-pattern/events-*) or index placeholder exists, events-index_pattern_placeholder (GET /_cat/indices)