Handle loading of blueprint with same StoreId as active blueprint

[emilk]

We stream-load all recordings and blueprints into a StoreBundle, which indices the stores based on StoreId.

This means that if we load a blueprint with the same StoreId as the current active one, we will progressively stream into the active blueprint, which can cause havoc on it. We only want to make a blueprint active once it is fully loaded.

A repro of this is to save a blueprint file, drag-drop it into the viewer, then drag-drop it once again into the viewer.

Current work-around

Each blueprint gets assigned a random store_id on save, which makes the chance of a store-id collision small.

There is also a warning printed if we still run into the problem.

Solutions A (the bad one)

Change store_id of blueprints as they load, or once they finish loading to something new and random.

Solution B (the slightly better one)

While loading blueprints, store then outside the main StoreHub/StoreBundle. Once they finish loading, move them into the main StoreHub.

Note that data recordings should still go into the main StoreHub because we stream those in.