Replace custom screen flow with standard declarative state-based react

[jchartrand]

Quite a bit of fairly complicated custom code is used to move through screens in the dashboard, seemingly using forward refs to show/hide screens, e.g.,

https://github.com/digitalcredentials/admin-dashboard/blob/main/services/payload/src/components/batch/RenderBatchFlowFields.tsx

The code seems intended to allow UI based configuration of screens at some point in time, but at the cost of significant extra complexity.

Given that there are no plans to add UI-based config, and since there are currently relatively few screens, it might be clearer to replace that code with standard declarative react - showing/hiding screens based on state variables.

A more conventional react-like model might make it easier for adopters to understand how to modify to suit their needs.