[BrowserSwitcher] Add metrics

This adds a handful of metrics:
- Number of navigations that trigger a switch
- Number of rules are in the various sitelists
- Time it takes to make a decision, on navigation
- Time it takes to start the alternate browser
- Success rate for alternate browser launch
- Whether the UrlList policy contains a wildcard

Bug: 898667
Change-Id: Ibc3d3d40725dcb84c685a9e59e3b28cd79ce860e
Reviewed-on: https://chromium-review.googlesource.com/c/1333872
Commit-Queue: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610956}