Requireable constraint tweaks & bugfixing

[jamiebrynes7]

Description

This PR makes some changes to when a field annotated with [Require] have IsValid set to false and the value set to null.

Previously this would only happen when a GameObject was unlinked from the underlying entity, typically when the entity had left the worker's view (unless a user had some custom logic). This means that if you had a MonoBehaviour like:

public MyBehaviour : MonoBehaviour {
    [Require] public HealthReader HealthReader;
}

if the underlying Health component left your view, say through a QBI query the HealthReader field would be left injected and IsValid would still be true. If you copied the reference or captured it in a closure, this could result in bad behaviour.

Now, when the required field's constraints are no longer met, HealthReader.IsValid is set to false and the MonoBehaviour's field is nulled out.

---

A consequence of this change in behaviour is that now if you have multiple required fields on a single behaviour, if one of them no longer matches the constraints, every field will be null-ed out and IsValid will be set to false

Tests

• Tests which cover the behaviour with a single field on a MonoBehaviour.
• Tests which cover the behaviour with multiple fields on a MonoBehaviour.
• Tested the FPS with multi-worker.

Documentation

• Changelog

[jamiebrynes7]

Tested against FPS w/ multiple workers. Seemed to work as expected. Will write up a changelog entry.