Fix encoded image being suggested for non-image blobs (like video)

[Wumpf]

What

Before:

After, the button is greyed out.

Made sure images still work fine by dragging in an image.

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[emilk]

Great!

[emilk]

Not new to this PR, but I think there is room for improvement of the naming of these things, maybe:

Suggested change

	fn update_applicability(&mut self, event: &re_chunk_store::ChunkStoreEvent) -> bool {
	diff_component_filter(event, |media_type: &re_types::components::MediaType| {
	media_type.is_image()
	}) || diff_component_filter(event, |image: &re_types::components::Blob| {
	MediaType::guess_from_data(&image.0).map_or(false, |media| media.is_image())
	})
	}
	fn is_applicable(&mut self, event: &re_chunk_store::ChunkStoreEvent) -> bool {
	is_any_component(event, |media_type: &re_types::components::MediaType| {
	media_type.is_image()
	}) || is_any_component(event, |image: &re_types::components::Blob| {
	MediaType::guess_from_data(&image.0).map_or(false, |media| media.is_image())
	})
	}

Also, does this really need &mut self?

anyway, no need to fix now. Just thinking out loud.

[Wumpf]

I'm not gonna change the trait and all associated implemenations now in this PR ;)

The semantics of update are correct and very relevant as this is an incremental and stateful update of the applicability. Details are on the trait's documentation

[Wumpf]

&mut self is for convenience if a trait implementor wants to track additional data that influence applicability