Allow to run rules using scheduler to avoid "Failed to execute rule ‘{}' with status '{}'" error path

[OlegAndreych]

I propose to use org.openhab.core.automation.internal.TriggerHandlerCallbackImpl#getScheduler when calling scripts to resolve an issue with simultaneous executions, as it is done for "normal" rules execution path.

That's needed for a code reuse using UI scripts.
Many rules are triggered with events with no known intervals and/or timing, so there's no sensible way to spread executions of these rules, so that they don't call scripts simultaneously.

An example of an issue can be found there: https://community.openhab.org/t/simultaneous-calling-of-script-problem/140087.

[rkoshak]

This might amount to a breaking change, though it breaks in a way that may not impact anyone.

Right now when one rule calls another, the calling rule blocks until the called rule returns. If I understand this PR correctly, that won't be the case any longer. The call to run the other rule will immediately return instead of blocking, which could break end users's rules if they are depending on this blocking behavior.

[OlegAndreych]

Note: we've discussed previous comment in the issue #4072.