Built-in scheduler should consider changes to missing intervals due to signals

[plaflamme]

Assuming the following:

MODEL(name full_with_signal, kind FULL, cron '@daily', signals=[(kind=SomeSignal)]);
select * from external_table

and

MODEL(name other_full, kind FULL, cron '@daily');
select * from full_with_signal

When the scheduler runs and both models have a missing interval, then they will correctly execute in sequence, allowing other_full to take into account the data in full_with_signal.

If the signal on full_with_signal determines that the interval is not yet ready, it will correctly be skipped by the scheduler, but the interval for other_full will still be computed in that run. In a subsequent run, the signal becomes ready and the interval for full_with_signal is computed, but now we're in a situation where they have run in the reverse order, making other_full not take data from full_with_signal into account.

The built-in scheduler needs to consider changes to missing intervals made by signals.