Extract sprites into a Vec

[ickshonpe]

Objective

Extract sprites into a Vec instead of a HashMap.

Solution

Extract UI nodes into a Vec instead of an EntityHashMap.
Add an index into the Vec to Transparent2d.
Compare both the index and render entity in prepare so there aren't any collisions.

Showcase

yellow this PR, red main

cargo run --example many_sprites --release --features "trace_tracy"

extract_sprites

queue_sprites

[alice-i-cecile]

@ickshonpe if you can get CI passing I'll merge this in for you :)

[JMS55]

@alice-i-cecile CI is passing now.