Goal is to include coverage of builtin functions into coverage
bitmap send to Fuzzilli fuzzer. In order to do this, after each
REPRL loop, coverage data of bitmaps are retrieved from JS heap
and stored into coverage bitmap. Additionally, there is an option,
to print out statistics about how many of edges from builtin
functions were turned on by the program inputted into REPRL loop.

This commit introduces two flags:
--no-fuzzilli-enable-builtins-coverage - when enable-builtins-coverage
 turned of, builtins coverage will not be exported to fuzzilli

--fuzzilli-coverage-statistics - when turned on, d8 prints
 statistics into covlog.txt file after each loop




Change-Id: I8f9cf8dc693b952467b108c6d6bc00134125bc5f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2263154
Commit-Queue: Peter Ralbovsky <ralbovsky@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68733}