Setup webgoat as a fixture in DAST end to end tests

What does this MR do?

The DAST end to end tests test_webgoat_full_scan previously would extract a TAR file to use as configuration for a WebGoat docker image that the test requires. This change checks in the extracted contents of the TAR file, as it is text anyway. Files that are changed each time by the WebGoat server are removed and ignored.

This change paves the way for an invoke task to be added to start/stop the WebGoat server for local testing. This has also been added in this MR.

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer