Cleanup: Harmonize main packages.

The vast majority of the main packages use main.go, so lets move these
two monitoring packages to that scheme as well.

Found with the following command line:

$ g grep "package main"  | grep -v main.go

BUG=None
TEST=None
R=jcgregorio@google.com

Review URL: https://codereview.chromium.org/715143002
Go with 'install' tool rather than using 'cp'.

Makes code more robust and puts it in sync with how we do elsewhere
(perf and monitoring).

BUG=skia:3083
R=jcgregorio@google.com

Review URL: https://codereview.chromium.org/722473002