ERL-625: stop EUnit on first failure

[OTP-Maintainer]

Original reporter: fenollp Affected version: OTP-21.0 Component: eunit Migrated from: https://bugs.erlang.org/browse/ERL-625

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Sometimes it is useful to end a unit test suite run as soon as a test fails.
An eunit option such as {fail_fast, boolean()}, defaulting to false would instruct eunit to cancel/skip all other tests on the first failure.

Note: another option that would help the development loop would be one that asks for the execution of a specific test via {only, Module, Function}.
If both Module:Function_test/0 and Module:Function_test_/0 do not exist, fail.
Otherwise run only either of these tests that exist and show the rest as skipped.