Improve `RawResourceStorage` in Worker

[mattrent]

• Improve error handling in get(), since right now it returns every error as a :resource_not_found
• Implement a RAM-based storage, to be used depending on the worker's preferences
• Add an option to cache functions (compiled, not raw) on creation, depending on the worker's preferences. This would save us even the "cold start" caused by the resource provisioning, but would require more RAM and "waste" more resources