Rename "no IR" stuff to reflect reality

This stuff all just punts to the interpreter, and there isn't such a
thing as a no-IR translation anymore, so let's clear this up.

I started thinking that maybe one of these steps isn't strictly
necessary. Currently, when we take a "slow" exit trace, we make a
RETRANSLATE_INTERPRET service request, which ends up creating a
"translation" that is nothing but an INTERPRET service request. This
feels like one more step than necessary; I think ideally we'd write out
an INTERPRET service request right in the exit-slow trace, but the
trouble right now is that at the point where we need to write it, we
don't know how many instructions should be interped.

Differential Revision: D925897
__get should be allowed for invalid properties

- Consistency with PHP, __get of an invalid property should
return an empty string instead of fatal

Closes #951

Differential Revision: D925220
pull fixup outside of translator-x64

- pull fixup/sync code outside of translator-x64
- push codeblock related functions from asm-x64 down to codeblock to
  enable this

Differential Revision: D924632