:recycle: Collapse async-tiff tile decode into single flat_map_iter call
No need for separate `.flat_map` and `.map`. Can coerce Bytes into u8 directly apparently. Still need to figure out if there's a more efficient way of multi-threaded decoding to raw bytes though.
:green_heart: Add criterion_benchmark func to benches/read_geotiff.rs
Can't be too empty. Also renamed ci.yml to bench.yml and explicitly set mode: instrumentation on CodSpeedHQ/action.