GetBrowserStateType added to iOS browser state metrics.

A function is added to iOS browser state metrics to return browser
profile type given web state.

Bug: 966747
Change-Id: I3f00212bb875ba010ea98e3b9db71dd2fb082b57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1690577
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676385}