Delete legacy lint and unit test engines

Summary: We've moved to comprehensive linting and unit testing, no need to maintain the individual ones anymore.

Test Plan: None.

Reviewers: ablackwood, jmillard, gbeaman, mportune

Reviewed By: ablackwood, jmillard, gbeaman, mportune

Subscribers: mbishop

Differential Revision: https://devportal.imobile3.com/D11215