Use erts::process::ffi::process_raise for Exception::Runtime to support catch

[KronicDeth]

From https://elixir-lang.slack.com/archives/CMX4EGTBQ/p1596826454151600:

@bitwalker

@KronicDeth I just pushed a commit that provides the infrastructure to raise Erlang panics from the runtime, you can test it out with `erlang:fail/1`, but I would start converting code that returns `Term::NONE` to instead call `erts::process::ffi::process_raise`

@KronicDeth

`native_implemented::function` has the `native` return `Term::NONE` if the `result` returns an exception it passes through `Process#return_status`, which returns `Term::NONE` for both `Exception::System` and `Exception::Runtime`. I should use `process_raise` for both system exceptions when we need GC and for runtime when it will show up as an Erlang exception I can `catch`?

@bitwalker

`process_raise` is just for `RuntimeException`, intended to handle things that would normally raise `error`, `exit` or `throw` in Erlang code. For system exceptions we should probably just panic, since there are essentially no cases where such exceptions can be handled in any kind of sane way; but I can also modify the exception handling to permit another internal exception type that can be raised via `process_raise` for those if we need to go that route - we can discuss further. For GC, I need to spend some time looking deeper; but for now we can have the runtime return Term::NONE and have that indicate that a GC is required, since we don't need `Term::NONE` for signaling errors

@bitwalker

The other thing we should do for GC is store the words/bytes needed for the GC to be considered successful, so that when calling in to the runtime to GC, we know what the success criteria is; otherwise we have to have some kind of retry thing happening in the generated code, and it's much easier to have a single fallback that will kill the process if the GC cannot free enough space or allocate a new heap of sufficient size

[KronicDeth]

Resolved by #541, which made lumen_rt_full also use process_raise.