Dedup wasm blobs

[s8sato]

As is evident in the case of multisig, triggers for different authorities can have the same logic, and currently they each hold a full blob, which would be a waste of space.

Possible solutions I think of:

1. Let by-call triggers inherit the caller authority
2. Have a dedicated instruction to register to hash-to-blob map and let other instructions and transactions hold ExecutableRef