Multiple blobs on same entity leads to ambiguous UI

[grtlr]

Describe the bug

When logging multiple blobs to the same entity (yay tagged components) the "Save blob..." button is placed not within its archetype but all the way at the bottom.

To Reproduce
Steps to reproduce the behavior:

1. Log multiple blobs under different archetypes to the same entity.
2. Look at the selection panel

Expected behavior
The download button should be shown grouped within each corresponding archetype.

Screenshots (note the two "data" blobs)

[Wumpf]

this might lead us to a slightly architectural issue that we've been delaying on: those additional save blob buttons are, just like image & video previews, a bit of a hack on top rather than following a generic path.
Ideally we figure a way out to register some kind of archetype ui so we can solved this more generically

[grtlr]

@emilk somewhat related to what we discussed yesterday.

[Wumpf]

worst case we could just not show the button at all instead of showing several.