This adds ctx.storage.kv, which has methods get(), put(), list(), and delete(). All four methods have the same signatures as the same-named methods of ctx.storage except:

1. They return synchronously. No promises.
2. They require SQLite-backed DOs.
3. list() returns an iterable rather than a map, so you can process results as they are read and you can cancel the loop early.
4. The batch versions of get/put/delete are not supported, since the implementation just calls the non-batch versions in a loop anyway. You might as well loop from JavaScript.
5. They don't have the allowConcurrency nor noCache options since those don't make sense for SQLite. (Nothing stops you from passing these options anyway; they will be ignored.)
6. The allowUnconfirmed option is also absent, not because it doesn't make sense, but becaues we haven't actually implemented it for SQLite-backed DOs in general. Maybe we will eventually.
7. Obscure: If you get() multiple keys at once, the returned map now iterates in the order in which the keys were specified, rather than in alphabetical order. The old interface's alphabetical ordering was a historical quirk that required an extra sort operation. It had been maintained for backwards-compatibility, but probably nobody really cares about it, so the new interface takes the opportunity to skip the sort.

The name storage.kv nicely parallels storage.sql while avoiding any backwards-compatibility concerns. In the long term we should "deprecate" (but forever support) the old async methods.