Allow control over when workflow instances get persisted

In Elsa 2, the user can control when the workflow needs to be persisted as it executes. There are several modes:

- After every burst of execution
- After every activity

In Elsa 3, we need something similar. The user should be able to configure this behavior on the workflow definition level, but also on a more granular level. For example, some workflows don't require the instance to be saved after every step, but only at certain sections.

The easiest way would be to add an option to an activity that says e.g. "Persist", but perhaps there's an elegant solution that doen't pollute the activity with this setting (since not all workflow applications may require persistence in the first place).

This topic was raised in [this discussion](https://github.com/elsa-workflows/elsa-core/discussions/3532).