AbstractJavaVirtualMachine.getCommandLine() is currently stubbed out, can't retrieve CLI parameters for Pre-Unified log.

Describe the bug
The getCommandLine() method has been stubbed out with a TODO. See https://github.com/microsoft/gctoolkit/blob/1476fc128465991f2c531645c780d3ed7c865f2c/api/src/main/java/com/microsoft/gctoolkit/jvm/AbstractJavaVirtualMachine.java#L84

Expected behavior
Expected this method, or child override in PreUnifiedJavaVirtualMachine to return the command line string from a Pre-Unified log file.

Additional context
There is a pending issue for building the Command Line args for Unified logging here: https://github.com/microsoft/gctoolkit/issues/263 which states that retrieving the command line is supported for Pre-Unified log files. However, the AbstractJavaVirtualMachine.getCommandLine() method is not overridden in PreUnifiedJavaVirtualMachine so the Abstract method is used instead.

Not sure if this was stubbed out while waiting for issue 263 or an oversight.

Start in api/src/main/java/com/microsoft/gctoolkit/jvm/AbstractJavaVirtualMachine.java at getCommandLine(), then inspect PreUnifiedJavaVirtualMachine and the Pre-Unified log parsing path. Compare the expected behavior with issue #263, and verify that the command-line string is returned for a Pre-Unified log without changing the Unified logging work.