Tests: Generate HashMaps of maximum tree height

[sjakobi]

It would be reassuring to check that everything works as expected when we operate on HashMaps of maximum height.

It seems fairly simple to generate the necessary hashes, by inverting the bit order, e.g. turning 0b0...01 into 0b10...0.

[sjakobi]

It seems fairly simple to generate the necessary hashes, by inverting the bit order, e.g. turning 0b0...01 into 0b10...0.

Inverting the byte order would probably be good enough too. Example: 0x0...0F -> 0x0F0...0

[sjakobi]

base contains functions for bit reversal and byte swapping

It's weird that there is no bitReverse or byteSwap despite GHC.Exts containing the corresponding Word# versions though: https://hackage.haskell.org/package/base-4.21.0.0/docs/GHC-Exts.html#v:bitReverse-35-