Inspect the WebView provider package name to determine the channel. This
only works for Monochrome (on Android N+); stand-alone WebView uses the
same package across channels, and will still be reported as "unknown".

Move version_utils from metrics/net/ to metrics/, and move the
channel-checking code from chrome/browser/ to version_info/, so that
WebView can use them.

Split off the part of version_utils that depends on //ui/base, since
most users of version_utils don't need that part, and it pulls in a huge
tree of dependencies.

BUG=711084

Review-Url: https://codereview.chromium.org/2879703002
Cr-Commit-Position: refs/heads/master@{#477124}