Add newtypes for less safe serialization of Map / Set / etc?

[mgsloan]

A check was added here to ensure that Map / Set are ascending, disallowing construction of invalid Map / Set. https://github.com/fpco/store/pull/109/files#diff-9ead574b8096a8cfea1c3a95c0f964d1R290

One thing we should do is benchmark whether it's even worth it to do this vs just converting normally from list. It could be we're losing all the benefits of fromAscList.

Either way, should have a way to do the fast thing when the input is trusted.