Stop using tape for tests

[bnoordhuis]

Tape runs all tests in the same process. There doesn't seem to be a way to request process-per-test isolation.

Monkey-patching in tests ends up affecting other tests. I'm quite sure at least one or two bugs (hopefully only in tests) went unnoticed because of it so I propose we move away from tape.

[rvagg]

or we could stop monkey patching or do proper isolation with child processes as required

[richardlau]

Another reason to stop using tape -- The test failure in #1131 actually stopped the test execution dead in its tracks (i.e. no further tests were run), e.g. https://ci.nodejs.org/view/Node.js-citgm/job/gibfahn-citgm-smoker-more-platforms/118/MACHINE=aix61-ppc64/console

[NatalieWolfe]

Tap would be largely a drop-in replacement and runs each of the test files as separate child processes.

[gibfahn]

We already use tap for node-report, citgm, and npm, so it would probably make sense to use it here as well.

[rvagg]

moving to #1171