fix: commented out some test cases

[tomchon]

This pull request updates the tests/parallel_test/cases.task file to modify how certain test cases are executed, primarily by commenting out some test entries and adding new ones for direct execution without the pytest.sh wrapper. These changes affect both vtable and system-test related test cases.

Test case management and execution:

• Commented out the test case entry for vtable/test_vtable_query_cross_db_stb.py, preventing it from running in the current configuration.
• Commented out several system-test case entries for tsma.py, tsma2.py, decimal.py, and decimal2.py, which disables their execution through the pytest.sh wrapper.
• Added commented versions of the above system-test cases, preserving them for future reference or easy re-enabling.
• Introduced new test case entries for decimal.py and decimal2.py (and their variants) to be run directly with python3 ./test.py instead of using the pytest.sh wrapper, and marked them as inactive (n).