and replaced poll interval setting with a hardcoded poll interval.
The hard coded interval will be removed in a follow up change to make
use of cluster state API's wait_for_metatdata_version.
Before the auto following was bootstrapped from thread pool scheduler,
but now auto followers for new remote clusters are bootstrapped when
a new cluster state is published.
Originates from #35895
Relates to #33007
Martijn van Groningen
Jason Tedor