wasmtime implementation violates aliasing requirements

[pepyakin]

When wasmtime handles a call to host functions it uses a mutable pointer to the contents of FunctionExecutorState and linear memory. The problem arises when using the sandbox wasmtime reenters into the host handling routines and obtains the mutable reference to the same items again.

[Demi-Marie]

1. This is a wasmtime bug, unless we have unsafe somewhere.
2. Until we have suitable OS-level sandboxing, we should stick with wasmi for the sandbox for security reasons.

[pepyakin]

1. Yeah, there is a lot of unsafe used. Not always with a good reason, IMO. That (as well as this issue) should be addressed with executor: Migrate wasmtime backend to a high-level API #4686.
2. I think this is not relevant: The issue is still present even though we that wasmi is being used for sandbox. It just the implementation of the wasmtime executor backend spawns this issue.