Since we currently require at least 1 MB of code to be potentially
dead, we will never trigger GC for small modules.
This CL lowers the threshold to 64 kB (plus 10% of committed code
space), which has basically no effect on large modules, but ensures
that we also run GCs on small modules.

R=mstarzinger@chromium.org

Bug: v8:8217
Change-Id: Ie76787af5ec7deb2e335303c2a98b81aeae6d4ef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627341Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61798}