Redirect metrics.wikimedia.org to Wikimetrics

While the domain has been removed in
59eab3e4b248405d7a08dc3d7e5a35a7fa21d470, search engines and some old
documentation still refer to it. So we redirect any requests to those
domains to the replacement service “Wikimetrics”.

Since the certificate for metrics.wikimedia.org has not been upgraded
since the Heartbleed vulnerability, we cannot reuse the old
certificate, and hence only redirect http traffic for now.

Bug: 64276
Change-Id: I43f978ad3db8076951523a247a12a06a10a3f73e
Merge "Redirect metrics.wikimedia.org to Wikimetrics" into production