Calling FindIndexInScript performs a linear search on the script functions and can
take considerable time. With Bytecode flushing we will lose the function_literal_id
and have to call FindIndexInScript if we ever recompile the flushed function. This
can take a significant proportion of the recompilation time and has caused regressions
in rendering times for some web applications (e.g, 395ms in FindIndexInScript for 132ms
spent lazily re-compiling code).

To avoid this, add function_literal_id back into the SFI and remove it from
UnoptimizedCompileInfo. This will slightly regress memory usage (particularly
in cases where many of the SFIs are compiled), however it means we can remove
the FindIndexInScript function and avoid these long-tail regressions when
bytecode is flushed.

BUG=chromium:965833

Change-Id: Ia31e82eb6c871a6d698a518326a8555822a7a1d8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1669700Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62319}