Fix XCCDF support

[Honny1]

This PR fixes crashes when using the XCCDF report.

How to reproduce the problem: Use oscpa-report with XCCDF results.
For example: oscap-report < tests/test_data/xccdf-report.xml

The crashes were caused by a missing part of the if condition. To avoid this problem, I created integration tests with all test files. And I discovered problems:

• The first is that it is expected that the rule must be present in some of the groups.
• Missing selected rule definition, which should be a content issue that is fixed in later versions.

[jan-cerny]

How can we reproduce the crash?

How will you prevent the bug from happening in future again?

[Honny1]

Changes:

• Fixes variable typo,
• Adds XCCDF validation,
• Improves warning report,
• New test to verify if a given input file is a valid ARF or XCCDF report.

[Honny1]

Changes:

• Rebased on the main branch
• Changes before the last rebase:
  • Reduced content of XML file plant_catalog.xml,
  • Fixed typos in expectation docstring and warnings texts,
  • Removed support for XCCDF 1.1.

Nothing has changed since @jan-cerny's last comment.

[jan-cerny]

I have verified that it still works OK after the rebase.