Currently Spring Integration creates its own `TaskScheduler` bean if one
does not exist in the context yet. When we add `@EnableScheduling`,
Spring Boot auto-configures one for us, but this one comes with slightly
different options than the default in Spring Integration.
This commit makes sure that Spring Integration reuses the
auto-configured TaskScheduler if possible, regardless of the user
opting-in for `@EnabledScheduling`.
See gh-25109
c5491cfdd7