Fix: programmatic API cannot access retried test objects

[juergba]

Description

To re-run a failing test Mocha:

• clones the test for each attempt
• passes the test object of the final attempt to the reporter by emitting an EVENT_TEST_END
• DOES NOT: update the original runner's test array suite.tests with the latest test object

The result of Mocha's core reporters is correct, since they hook into events and use the latest test object. But third party reporters as Mochawesome relying on suite.tests may show incorrect test results.

Description of the Change

We update runner's suite.tests after the final attempt when the EVENT_TEST_END is emitted and replace the first failing test by the test object of the last attempt.

Applicable issues

closes #2188

[juergba]

@adamgruber @dcr007 could you grant this branch a test run, please?

[coveralls]

Coverage increased (+0.02%) to 92.877% when pulling 5395844 on juergba/retries into ac12f2c on master.