* IntMap: Merge prefix and mask in Bin

* Update lookupGE benchmarks

* Add note on the relation to the Okasaki-Gill paper

* Adopt BurningWitness's lower/upper helpers

* Add property tests for is{Proper}SubmapOfBy

* Generate large keys in Arbitrary IntMap for better coverage

* Add GHC flag to prevent benchmarks from changing due to unpredictable alignment changes