The following runtime functions (and their intrinsic counter parts) are
completely unused/obsolete by now

  - %ToInteger
  - %GeneratorGetInputOrDebugPos

and in addition the intrinsics for %_ToNumber and %_IsJSProxy are also
dead (according to code coverage and manual verification), so drop them
as well (their runtime function counterparts are still somewhat used).

Bug: v8:8015
Change-Id: I60d53762dd9717fb43de38cb490b46676c467212
Reviewed-on: https://chromium-review.googlesource.com/1235923Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56076}