test: move module out of fixture directory

tick-processor-base.js is a module used by three other tests. It is not
a test fixture so move it out of the fixture directory. (One downside to
having it in the fixture directory is that fixture code is not currently
linted.)

It is possible that the code in tick-processor-base.js should be
integrated into common.js. This can potentially happen subsequently (and
might make a reasonable good first contribution for a new contributor).

PR-URL: https://github.com/nodejs/node/pull/9022


Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>