build: run flaky tests in Travis

[Trott]

Continuation of #27015

Skipping flaky tests in CI is an anti-pattern that should be avoided,
as we do in our ownCI. Failing flaky tests don’t need to be blockers
for a green CI result, but they should be run and reported somehow.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[nodejs-github-bot]

Lite-CI: https://ci.nodejs.org/job/node-test-pull-request-lite-pipeline/3215

[refack]

IMO the travis run should be a minimal sanity test that returns results ASAP. For me test coverage is a non-goal. I'd go as far as advocating for skipping more tests, not less.

ATM a typical Travis run takes a minimum of 12.5 minutes:

of those only 3.5 are bootstrapping and compilation, so 9 minutes just for testing. Seems unproductive.
https://pythonspeed.com/articles/high-cost-slow-tests/

[Trott]

IMO the travis run should be a minimal sanity test that returns results ASAP. For me test coverage is a non-goal. I'd go as far as advocating for skipping more tests, not less.

Interesting. For me, finishing quickly in Travis is a non-goal. (Finishing quickly for local runs, however, is.) Making Travis as useful as possible is a goal, and that means not skipping tests we don't need to skip.

[refack]

For example this PR, 15 minutes after submission, our Lite-CI finished, and the Travis job hasn't even started
_{comments in screenshot were trimmed for emphasis of time and results}

[Trott]

For example this PR, 15 minutes after submission, our Lite-CI finished, and the Travis job hasn't even started

I just don't see that as a problem, to be honest. If tests aren't working in a Travis environment, they're probably not going to work for some users in some environments. So I want to know.

[richardlau]

Practically speaking this PR only affects a small number of tests. e.g. for #27164 our CI ran 2615 tests (https://ci.nodejs.org/job/node-test-commit-linuxone/nodes=rhel72-s390x/12353/) while the Travis run ran 2610 tests (https://travis-ci.com/nodejs/node/jobs/191674829#L1063). Five tests isn't going to make a huge difference to the overall running time.

[Trott]

Landed in 56354d4