TC-110123: Replace JAXB DatatypeConverter with JDK DatatypeFactory

[Shan-SmartBear]

Problem
On Jenkins running Java 11 or newer (Java 17 / 21, Jenkins LTS 2.555+), the plugin fails with: java.lang.ClassNotFoundException: javax.xml.bind.DatatypeConverter

The test run finishes fine (exit code 0). The error happens later, when the plugin reads the TestComplete log and builds the JUnit-style report. Jenkins then marks the build as FAILED.

Cause
The plugin used javax.xml.bind.DatatypeConverter.printDateTime() to make the timestamp. JAXB (javax.xml.bind) was removed from the JDK in Java 11. Old Jenkins versions still had it by chance; from LTS 2.555 it is no longer on the plugin classpath.

Fix
Replaced the JAXB call with javax.xml.datatype.DatatypeFactory, which is part of the JDK (JAXP) and is present in Java 8, 11, 17 and 21.

Jira: https://smartbear.atlassian.net/browse/TC-110123

Testing done

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed