Allow graceful error handling in `Simulator.throwException`

### Motivation

As it is currently implemented, whenever there is an `Exception` thrown via `Simulator.throwException`, the `Simulator.run` function will always throw the first exception and halt any remaining progress through the run function. It also will always log a `severe` message. Some implications:
- Only the first exception is made visible to the user
- Even if a user catches the exception, there is still a `severe` message which could cause test failures in ROHD-VF testbenches
- No end-of-simulation actions will ever execute

These seem like excessive limitations, and we should provide a method of gracefully handling issues from the `Simulator`.

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Additionally, if the `Simulator` is not actively running, then `Simulator.throwException` currently does nothing. This doesn't seem like proper behavior, and we should probably be immediately rethrowing in this case.

### Desired solution

A way to configure the `Simulator` to gracefully handle error before defaulting to `throw`ing it and incurring all of the downsides mentioned above. We can maybe look to the event handlers of `StreamSubscription` for inspiration: https://api.flutter.dev/flutter/dart-async/StreamSubscription-class.html

It should be possible to handle errors and still execute end-of-simulation actions.

Some thought needs to be put into how to log the messages in a way that is convenient for use cases like ROHD-VF.

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We should immediately rethrow exceptions passed to `Simulator.throwException` if the simulation is not running.

### Alternatives considered

_No response_

### Additional details

_No response_