The native flag is a left-over from self-hosted JavaScript. Currently
only the empty function and empty script are marked native.
This CL removes the native flag from the ParseInfo,
UnoptimizedCompilationInfo and its handling in the bytecode generator.

R=leszeks@chromium.org

Bug: v8:8834,v8:9043
Change-Id: I60726e28ce83cc84249e9c49bdc88d81f0a695c9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1545079Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60606}