Adds a /metrics page with Chart.js charts, which requires an annoying
CDN fetch but until I figure out a good method of fetching things during
build it's our best bet. I've pinned the thing so it's probably good.
The page displays build counts, duration percentiles and system
distribution. Time range and project filters are included, and the
metrics page is linked from navigation.
Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I99059594c29a9b35d2fd4d140628d6f46a6a6964
