plutus-tx: add red-black tree implementation for Maps, again

[michaelpj]

It still sucks. It manages to sometimes be better, which is cool, but overall it's quite a lot worse and it uses a lot of space. So still not worth it unless we somehow figure out a way to make it much faster.

Amusingly, with this version the dumb equality function is almost as good as @effectfully 's clever one. Also toList produces an ordered list, so maybe we could optimize equality further, IDK.

I spent a bit of time on it to get it this fast, mostly fusing things together so we don't do multiple passes. biFoldr is the workhorse.

Some things I have not tried:

• Pass around k -> k -> Ordering instead of Ord k, since apparently our Ord class has a ton of members
• Manually specialise to ByteString keys
• Come up with a fast way to iterate through the entries of two maps in order without either materializing them into lists or doing lots of lookups (which is what the current biFoldr does effectively by calling split)
• Actually profiling to see what's happening instead of just looking at it.