Cache decrypted state to improve performance

[Mrtenz]

Snap state (managed through snap_manageState) can be cached in memory to improve performance, and avoid decrypting multiple times.

[FrederikBolding]

@Mrtenz We should wipe the cached state when the client is locked, similarly to KeyringController

[FrederikBolding]

Also worth it to loop in @naugtur to potentially with exploring some obfuscation techniques

[naugtur]

How critical is the data that's getting cached?
What's the size of that data?

[Mrtenz]

How critical is the data that's getting cached? What's the size of that data?

@naugtur It's arbitrary data from any snap. It could be private keys, or just user preferences, etc. It can be anywhere from a couple kilobytes up to 100 MB IIRC.