GitLab

Convert the //net/dns:public source_set into :host_resolver and move all
public headers to source.  Access to these previously-public headers
will now only be allowed for BUILD.gn rules listed in the friend list.

Added friend entries with explanation comments for all remaining usage.
Some with TODOs to remove, eg because they'll be migrated to network
service.  Confirmed that there are no other remaining usage in code
where private headers are or are not enforced (checking unenforced by
searching for "net/dns" in the error output).

Removed a couple includes that were no longer needed.

TBR=jochen@chromium.org

Bug: 846454
Change-Id: I7bb633088689dc896f9fc27e1dec87ae699410db
Reviewed-on: https://chromium-review.googlesource.com/1183981
Commit-Queue: Eric Orth <ericorth@chromium.org>
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586362}