Common Helper classes and methods for Unit/Integration testing

As a **developer using Fluxity**,

I want **testing helper classes/methods**,

So that **I can test my Fluxity process quickly and easily**.

## Description

Add classes/methods that can be used in a test suite to test Fluxity-related implementations.

Examples:
- An IDispatcher which can be used in unit/integration tests which keeps a record of Commands dispatched
- As above but can also Dispatch normally
- An Initializer which can be made independent of the Unity lifecycle

## Acceptance Criteria

- Additional testing features added

### Additional context