Handle Python 3.12 deprecation warnings

[tcalmant]

From CI:

• EDEF parser must change the test of existence of XML elements

tests/rsa/test_edef.py: 86 warnings
tests/rsa/test_rsa.py: 77 warnings
tests/rsa/test_shell.py: 48 warnings
  /home/runner/work/ipopo/ipopo/pelix/rsa/edef.py:253: DeprecationWarning: Testing an element's truth value will always return True in future versions.  Use specific 'len(elem)' or 'elem is not None' test instead.
    if element:

• Tar extraction API will change

tests/rsa/test_py4j_tutorial.py::Py4JTutorialTest::test_service_import
  /home/runner/work/ipopo/ipopo/tests/rsa/test_py4j_tutorial.py:93: DeprecationWarning: Python 3.14 will, by default, filter extracted tar archives and reject files or modify their metadata. Use the filter argument to control this behavior.
    tar.extractall(path, filtered_members, numeric_owner=numeric_owner)

• utcnow() is deprecated

tests/shell/test_report.py: 26 warnings
  /home/runner/work/ipopo/ipopo/pelix/shell/report.py:608: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
    "time.utc": str(datetime.datetime.utcnow()),

[tcalmant]

Fixed in #135