Log events when user views campaign preview and create/updates campaign

Created by: mrnugget

This fixes https://github.com/sourcegraph/sourcegraph/issues/15482 and is the client-side portion of it. The backend portion is in https://github.com/sourcegraph/sourcegraph/pull/15279.

@dadlerj @ebrodymoore Since this only logs events I wasn't sure about how to document this, but I added it to the ping-data pages.