Support one-time `@Scheduled` tasks

[marceloverdijk]

As discussed here #31210 it would be useful to be able to only specify an initialDelay for @Scheduled task to run in only once. So without cron/fixedDelay/fixedRate to be specified.

[marceloverdijk]

Some background.

Many used something like @Scheduled(initialDelay = 5, fixedDelay = Long.MAX_VALUE) for this, but that resulted in an unexpected ArithmeticException in 6.0.10 (#30754).

This was fixed in 6.0.11 but in other cases like @Scheduled(initialDelay = 5, fixedDelay = Integer.MAX_VALUE, timeUnit = TimeUnit.MINUTES) this still happens.

So it would be nice to be able to configure an one-time task without setting a fixedDelay in a very far future.

[marceloverdijk]

Thx @jhoeller that was fast ;-)