Add a user-configurable cap on the amount of memory that is gathered by
dereferencing thread stacks. (SyzyAsan stores a tremendously large
number of pointers on the stack, so the dumps were ending up in the ~25M
range.)
Also reduce the range around pointers somewhat.
Change-Id: I6bce57d86bd2f6a796e1580c530909e089ec00ed
Reviewed-on: https://chromium-review.googlesource.com/338463
Reviewed-by: Mark Mentovai <mark@chromium.org>