GitLab

- remove many now-fixed issues, update open issues
- things basically work now, so recommend using trunk lld less strongly
- add section with pointers on how to make repros

Bug: 1149587
Change-Id: I4524c99c4894b1669a4d12dfcda677b31fea491c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611444
Commit-Queue: Nico Weber <thakis@chromium.org>
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840270}