Test duration in JUnit reports

**User story**
As a tester, I want to see test durations in the JUnit reports so that I'm able to see how my SUT behaves during stress tests.

**Additional context**
The report templates for [testsuites](https://github.com/citrusframework/citrus/blob/8bdf243e1691c591777b7c23d545a33812885ab8/core/citrus-base/src/main/resources/com/consol/citrus/report/junit-report.xml#L2) and [testcases](https://github.com/citrusframework/citrus/blob/8bdf243e1691c591777b7c23d545a33812885ab8/core/citrus-base/src/main/resources/com/consol/citrus/report/junit-test.xml) already contain the attribute `time`, whose value is provided by the property `test.duration`. However, `test.duration` is set to `0.0` for both [testsuites](https://github.com/citrusframework/citrus/blob/8bdf243e1691c591777b7c23d545a33812885ab8/core/citrus-base/src/main/java/com/consol/citrus/report/JUnitReporter.java#L143) and [testcases](https://github.com/citrusframework/citrus/blob/8bdf243e1691c591777b7c23d545a33812885ab8/core/citrus-base/src/main/java/com/consol/citrus/report/JUnitReporter.java#L116).

Start with core/citrus-base/src/main/java/com/consol/citrus/report/JUnitReporter.java at the testcase and testsuite handling referenced in the issue, then compare the junit-report.xml and junit-test.xml templates. Trace how test.duration is populated and verify that generated JUnit reports contain the actual test durations instead of 0.0.

Written by the indexing model from the issue text.