Input System Focus Provider implementation registers its own implementation instead of through configuration

[SimonDarksideJ]

Reality Collective - Reality Toolkit Bug Report

Describe the bug

Currently, the Focus Provider is Registered manually by the Input System during instantiation (Constructor), which is not the correct behaviour as services "should" be registered through configuration alone.

As part of the Service Framework implementation, this caused issues because it was trying to register a data provider as it was being created but before it was registered, this caused the focus provider instantiation to fail because its parent service (the input system) was not actively registered yet.

This needs a better implementation whereby the focus provider is recognised in the configuration and instantiated along with other data providers once its parent system is active.

Expected behavior

Data Providers should be instantiated once their parent services are registered.

Actual behavior

The Focus data provider is trying to register before the input system, during the class instantiation of the Input System.