Simplify state management

Child components use the pinia store. These components are not reusable outside the context of modifying or launching an instrument, so they can be tightly bound to that state without increasing complexity or reducing maintainability. This allows us to get rid of a decent amount of property passing.

Saving doesn't currently work, but I think it's on the API side, it seems some field name translation is confused somewhere along the pipeline, translating between snake_case and camelCase. I suggest we use snake_case everywhere, even in js.

Bug: T366759