Enable DWARF4 line numbers in non-debug builds when symbol_level > 0.

This is a reland of commit a4b0fa8dccba2326ea7a5047a3b30ca7a5f0c7d4. The
original CL was reverted because death tests timed out in debug builds,
since the performance of line number extraction is very sensitive to
optimizations. To avoid that, line number extraction is disabled by
default in debug builds.

The original CL also includes a fix to skip over stack frames that do
not have a corresponding object file to open.

Bug: 1039359
Change-Id: Ida11e8ba04859db87382a6aa4290460b7e325ec4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5329237
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1268213}