[LayoutNG] Simplify & correct static position for OOF positioned.

This patch is primarily simplifies how we determine the static position
for an OOF positioned node, within the inline context.

There are many fixes, (see test cases).

Additionally, fixed positioned nodes, now work when they have an inline
level containing block.

Bug: 636993
Change-Id: I36b573578fc85d9ba9b757f258ec7391eec73c0a
Reviewed-on: https://chromium-review.googlesource.com/c/1356999
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Aleks Totic <atotic@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614426}
32 files changed