Expose an enumerable key/value store persistence API

[danfinlay]

Some snaps and use cases require more data than a single JSON blob, and efficient performance depends on such a snap's ability to minimize how much storage is kept in memory.

Examples:

• A light-client
• A swingset
• A data caching layer, like ipfs or a DID registry.

In particular, I was thinking of making a resumable swingset as a snap. This would greatly benefit from being able to store transactions in a re-enumerable order, the way IndexedDB would let me do.

This might work if you just wrapped the IndexedDB API in a way where all keys were force-prefixed with a secret key that is unique to the requesting snap. IndexedDB is available to both node and browser, so it might be a suitable API to expose (attenuated).

[FrederikBolding]

API-wise you can use snap_getState and snap_setState as a KV now 🫡