Updated suborigin serialization to latest spec proposal

This modifiest the serialization format of suborigins so they are now
represented in the form https-so://suboriginname.host.name (or,
alternatively, with the scheme http-so). This change removes collisions
with potentially valid URLs that were being deserialized as suborigins.

Additionally, this adds suborigins back as an experimental web platform
feature rather than a testing feature.

BUG=336894
R=mkwst@chromium.org

Review-Url: https://codereview.chromium.org/2332263002
Cr-Commit-Position: refs/heads/master@{#420828}
29 files changed