[tools] Add a tool for finding builtins

Example usage:
    tools/find-builtin LoadIC | xargs code -g

Change-Id: I12c15d3d4a80edbcddfa9cc8b9a515b839c96fdf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2808949


Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73827}